Withdrawal symptoms: party factions, political change and British foreign policy post-Brexit

ABSTRACT
 The effects of Brexit on British foreign, security and defence policy have been complex. Initial efforts to agree structured cooperation failed, with later governments refusing to negotiate on this area, followed by unstructured re-engagement after Russia’s invasion of Ukraine. This article argues that these changes can be explained by reference to the factional politics during the Brexit negotiations within the Conservative Party, with the defeat of May’s Withdrawal Agreement bringing to power a pro-Brexit faction with a distinct foreign policy worldview and incentives to demonstrate a cleaner break from the European Union. Empirically, the article draws on a series of interviews conducted with UK and EU policymakers. The findings demonstrate the significance of ideology and party factions in a policy domain where the UK is powerful enough to treat EU institutions as useful rather than necessary, and shows the direct and indirect ways factional politics brings about external change.


Introduction
Understanding the impact of Brexit on the United Kingdom's (UK) foreign and security policy is made more complex by the extent of variation following the June 2016 referendum.The May government attempted to ensure a high degree of underlying continuity in foreign and defence policy, maintaining strong relations with key European allies and seeking a comprehensive partnership with the EU in foreign and security policy, which appeared to show a renewed UK interest in European structures.The Johnson government, however, undertook more substantial changes in development and defence policy, presided over deteriorating relationships with European allies (especially France), and opted not to negotiate a security agreement with the EU, a position that remained unchanged even following the Russian invasion of Ukraine in February 2022.
Accounting for these changes by reference to existing theoretical perspectives is not easy.Structural accounts (e.g., Cladi & Locatelli, 2020;Turpin, 2019) which invoke the degree of external threats or strength of the Transatlantic alliance as determinants of foreign policy change cannot explain why the Johnson government declined a security agreement in the face of a Trump Presidency and growing fears of Russian revanchism.Partisan perspectives (e.g., Hofmann, 2013) similarly find it difficult to account for the diverse policies of two Conservative Prime Ministers, both of whom made delivering Brexit their core policy priority.Moreover, accounts rooted in the Brexit process itself and the (limited) nature of the models on offer (e.g., Svendsen, 2021;Wessel, 2019) cannot help us understand the variation on the UK side, since the eventual outcome of the non-negotiated framework was never known.Individual approaches focusing on the differences between May and Johnson potentially fare better, but risk lapsing into ad hoc forms of explanation and ignoring broader dynamics in British politics.
This article argues that the changing foreign and security policies of successive governments post-referendum can be understood only in relation to the underlying factional politics within the Conservative Party during this period.To show this, the article draws on several semi-structured interviews conducted with policymakers, political actors and former officials in London and Brussels from 2017 to 2023.The empirical discussion demonstrates that divisions over hard and soft designs on Brexit were exacerbated during the course of the negotiations, leading ultimately to a showdown in early 2019 and the ascendency of a more traditionally Conservative faction of the party in July 2019 under Johnson.Understanding the factional politics underpinning British foreign and security policy post-Brexit highlights significant temporal variation in recent years which is poorly captured by overarching framings applied to the period (e.g., 'Global Britain').Theoretically, a focus on party factionalism shows the importance of taking ideology into account when seeking to understand the direction of foreign policy, and helps identify those aspects of domestic factional conflict responsible for re-politicising foreign policy issues.
The article proceeds as follows.The first section examines the growing literature on political parties in International Relations (IR) and Foreign Policy Analysis (FPA) to make conceptual space for understanding the relationship between factional politics and external policymaking.The subsequent empirical discussion of UK foreign and security policy post-Brexit is divided into four periods: (1) An overview of the British foreign policy tradition and the role of EU foreign and security policy initiatives within it; (2) Theresa May's tenure in office, from the aftermath of the referendum to her resignation in July 2019; (3) Boris Johnson's initial years in office during which the TCA was negotiated; and (4) the period following Russia's invasion of Ukraine.The article concludes with a discussion of current developments and a summary of the empirical and theoretical value of taking factional politics seriously.

Parties and party factions in foreign and security policy
Recent years have witnessed increased attention to the role of political parties within the disciplines of IR and FPA (e.g., Chryssogelos, 2020a;Haesebrouck et al., 2022;Hofmann & Martill, 2021;Otjes et al., 2022;Rathbun, 2011;Raunio & Wagner, 2020).The increased interest in parties reflects broader inter-related changes in international politics in recent years, which have made party competition more important, including the gradual parliamentarisation of foreign and security policy (Neal, 2020;Wagner et al., 2017), the increase in competences of actors at the international level that touch upon distributive and 'domestic' issues (Chryssogelos, 2020b), the backlash against neoliberal globalisation (Noël & Thérien, 2008), the rise of populist parties (Destradi et al., 2022), and the emergence of a more diffuse multipolar order with a greater choice of potential alliance partners (Hofmann & Martill, 2021, p. 320).Recent research on parties in particular has advocated a move beyond the question of whether parties matter in foreign policythey clearly do at certain timestowards further consideration of the ways in which parties matter and the conditions under which they are most influential (Hofmann & Martill, 2021;Raunio & Wagner, 2020).
One reason political parties do matter for foreign and security policy is in their role as vehicles of ideology, including distinct philosophies of international relations with correspondingly diverse interpretations of the 'national interest' (Jackson, 2022;Hill, 2019).This is not to say ideology is the only link between parties and foreign policysome accounts focus rather on vote-seeking behaviour (Davidson, 2008), temporal dynamics and the electoral cycle (Aldrich et al., 2006), and patterns of constituency interests (Trubowitz, 1998) but it is one area where variation between parties is clearly observable.For instance, parties of the right tend to be more sceptical of multilateralism (Rathbun, 2011), more supportive of the use of force (Fonck et al., 2019), more favourably disposed to Atlanticist (rather than European) defence structures (Hofmann, 2013), less supportive of parliamentary control of foreign policy (Wagner et al., 2017), less predisposed to high levels of foreign aid spending (Thérien & Noël, 2000), less supportive of humanitarian intervention (Hildebrandt et al., 2013), and possessive of a reduced scope of moral concern (Gries, 2014, p. 81).On some issues both left and right have found themselves opposed respectively to the liberal centre, including European integration (Hooghe et al., 2002), support for the liberal international order, and Cold War strategy (Martill, 2019).
Partisanship can vary both within and between parties, depending on the balance of opinion across the political spectrum and the mapping of parties across this distribution.Factionalism emerges when distinct organisational and ideologically-bounded constituencies emerge within a broader party.Within majoritarian systems, factionalism can be more prominent, since the electoral system is geared towards producing bipolar partisan competition with broad parties comprising multiple constituencies of thought (Clare, 2010).Where single party government is the norm, intra-party conflict can be the most prevalent form of opposition to the government's agenda (King, 1976).In some instances, like the backbench 1922 Committee in the UK, or the CERES faction within the French Socialist Party, factions can be highly institutionalised and operate as a 'party within a party' (Russell, 2021, p. 452).In other cases, factions may be more ad hoc, arising on individual issues or in a looser and more uncoordinated manner.The influence of factions depends on several factors, including their organisational capacity and bureaucratic resources, the degree of coordination and strength of the leadership, the size of the government's majority and its ability to form alliances outside the party, and the available mechanisms for parliamentary oversight (Neal, 2020).
Whether factional divisions emerge on foreign policy issuesand whether they can be consequential if they dodepends on the attributes of the state in question and the nature of the foreign policy issue.Where issues are highly securitised, or where actors find themselves in weakened or asymmetric positions, few alternative courses of action may be available, rendering factional competition either non-existent or moot.In contrast, where states are more powerful they have far greater leeway to pursue multiple options in their foreign and security policy (e.g., Weiss & Edwards, 2022).Moreover, factionalism can be more efficacious where greater choice exists externally, for instance where there are multiple potential alliance partners or where the existence of multiple overlapping institutional frameworks allows for forum shopping among members (Hofmann, 2011).

British foreign policy and European integration
Britain's role in the world is often defined in relation to its former hegemonic role and the difficulties of decline over the decades since (especially) the Second World War, which greatly weakened the UK's relative capabilities.And yet Britain retains aspects of its former role as a 'residual' great power, including a permanent seat on the UN Security Council, sizable military capabilities including the nuclear deterrent, and a formidable diplomatic network (Whitman, 2016b).Britain's alignments variously comprise the Anglo-American 'special relationship', London's leading role in the Commonwealth, and the country's former role as an EU member state, and while distinct facets have been prioritised at various times, successive prime ministers have invoked Britain's ability to link these domains as an important facet of its global influence (Oliver, 2020).In the broadest sense, UK foreign policy goals are liberal ones, with a heavy emphasis on human rights, democracy promotion, development aid, and institutional creation (e.g., Beech, 2011;Whitman, 2016b), with little deviation from these in the post-war period.Indeed, it was common to speak of a post-war consensus in UK foreign policy on Britain's international role, its grand strategy, and its relation with the US (e.g., Addison, 1998;Dobson, 1990), although in recent years more significant divisions have emerged on Europe and on military intervention (Fonck et al., 2019).
The evolving relationship with the EC/EU and gradual emergence of European-level foreign and security policy cooperation has altered the means by which Britain has articulated its interests.Accession itself was motivated partly by economic underperformance but also by claims that EC membership would enhance Britain's diminished voice in international politics (Hill, 2019;Saunders, 2020).When Britain acceded to the EC in 1973, European Political Cooperation (EPC) was in full swing, with six-monthly Foreign Ministers' meetings helping to establish common European positions on the CSCE process and the Falklands War.By the mid-1990s, initial UK scepticism towards a security and defence role for the EU wavered in response to inaction in the Balkan Wars and political change at home (under New Labour), leading to the Anglo-French St Malo declaration of 1998 and the creation of the Common Security and Defence Policy (CSDP) (Hofmann & Mérand, 2020).Divisions within Europe over the question of support for the US-led Iraq War in 2003 did not prevent the operationalisation of the CSDP, with the first operations in that year (Menon, 2004), although British interest in the EU as a platform for deployment failed to keep up with London's initial enthusiasm for the project (Turpin, 2019).
The CFSP and CSDP both were viewed by UK officials as helpful additions to the UK's foreign policy toolkit.CFSP meetings provided for a 'coordination reflex' between EU member states which allowed for a more distinct European role on issues where transatlantic divisions existed (such as on Iran) while the CSDP enabled Europeans to take on the burden of regional crisismanagement where the US held less of a stake.In this sense, London has always viewed EU security policy as a complement to NATO and to the numerous other bilateral and mini-lateral arrangements in the European security architecture (Hofmann, 2011), and has vetoed in the past proposals to extend EU competences in the defence domain (Bérard-Sudreau & Pannier, 2021).The distinctive nature of the CFSP/CSDP within the EU decision-making system, based on intergovernmental decisions in the Council and with little role for the Community institutions (the Commission, the Court, the Parliament), made participation relatively cost-less in sovereignty terms (Turpin, 2019).In this manner, European foreign policy cooperation can be seen more as a means of managing differences between member states, rather than imposing a homogenous EU position (Maurer & Wright, 2021), with Britain viewing EU-level cooperation as an 'optional extra' rather than the master framework for its foreign policy (Whitman, 2016a).
Britain's vote to leave the EU in the June 2016 referendum upset this equilibrium.Even though the CFSP/CSDP was predominantly intergovernmental and owed its inception to an Anglo-French diplomatic push (Hofmann & Mérand, 2020), participation in the CFSP/CSDP is tied to EU membership, with few available forms of association for third countries (Svendsen, 2021;Wessel, 2019).Without an agreement covering security and defence issues, however, Britain and the EU both stood to lose out.The EU could not count on the contribution of the UK's sizable military, economic and diplomatic resources, while the UK would not be able to coordinate its position with the EU27 or upload issues of concern to the European level (Hill, 2019;Sus & Martill, 2019, pp. 31-33).Whether Brexit would have implications for British foreign policy outside the ability to access the CFSP/CSDP was a more open question.While security policy had featured little in the referendum campaign and was not on the list of renegotiation priorities (Hill, 2018(Hill, , 2019;;Whitman, 2016a), broader themes of British globality and 'greatness' had a significant presence in the Leave campaign's materials (Rogstad & Martill, 2022), conveying distinct preferences within Leave-supporting constituencies for re-prioritising Britain's extra-European partners post-Brexit, including (variously) the United States, the Commonwealth, the 'Anglosphere', and emerging powers (Bell & Vucetic, 2019;Gamble, 2021;Namusoke, 2016;Oliver, 2020).

Post-Brexit continuity under Theresa May
Theresa May's tenure in office was defined by her ultimately unsuccessful efforts to deliver on the mandate established by the 2016 referendum.Upon assuming office, the new Prime Minister confronted the difficult task of deciding what Brexit should look like and how it might be implemented.This was made all the more difficult by the extent of intra-party divisions, with pre-existing Conservative schisms on the Europe questions translating into opposing positions on 'soft' and 'hard' designs for Brexit (Aidt et al., 2021, p. 592).On the right, the European Research Group (ERG) comprised the most organised faction, a cadre of around 80 MPs who supported a more distant relationship with the EU, while many of those MPs who had backed Remain in 2016 supported closer alignment post-Brexit (Stimmer & Glaserman, 2022).While the moderates generally accepted the referendum result, they sought an outcome that minimised the disruption from Brexit and maintained significant aspects of the status quo, including keeping UK close to the CFSP/CSDP (Tannock, 2017).In contrast, the pro-Brexit right saw EU initiatives as superfluous and preferred an exclusive focus on NATO for security policy and realignment towards Britain's global partners (Owen, 2016).
The May government's positioning vis-à-vis the two factions is complex.Owing to the dynamics of the UK party system, and May's own fierce loyalty to the Conservative Party, it became clear early on that the prime minister would prioritise internal unity over efforts to engage with the political opposition.This meant that delivering Brexit would require May to bridge the schisms between the warring Conservative factions, since Labour support was unlikely to be forthcoming (Russell, 2021, p. 450).The government's loss of its parliamentary majority in the June 2017 general election exacerbated these difficulties, forcing the government into a confidenceand-supply arrangement with the pro-Brexit Democratic Unionist Party (DUP) and decreasing the scale of intra-party dissent required to undermine the government's policies (Baldini et al., 2022, p. 336).One consequence of this was that the government was subject to a significant number of legislative defeats during the 2017-2019 parliament, as Conservative backbenchers rebelled to vote alongside Labour in support of amendments which would increase Parliament's say over the final deal (Giuliani, 2021;Martill, 2021).
May's broader designs for Brexit aimed at ensuring the maximum degree of continuity in the economic relationship compatible with the government's own strict 'red lines'.When articulated in the Lancaster House speech in January 2017, the 'red lines' seemed to signal that May would be seeking a reasonably hard Brexit, since they would rule out most alternative forms of association except for a simple Free Trade Agreement (FTA) (HM Government, 2017).Yet May's intention was not to preclude these alternative outcomes, but to use these constraints as a basis for seeking a new, bespoke arrangement with the EU, whichif it succeeded in maintaining continuitywould appeal to both sides of the Brexit debate.This proved unrealistic, based as it was on a misreading of the EU's interest in defending the integrity of the Single Market and the existing balance of rights and obligations (Schuette, 2021).Regarding Brexit as an existential crisis for the Union, the EU27 committed from the earliest stages to a position that maintained internal unity (Interview 1), opposed efforts to 'cherry pick' access to EU policies (Interview 3), preseved the Union's autonomy of decision-making (Interview 2), and offered variants of 'off the shelf' models of association (Interview 4).With the EU27 more powerful collectively (Laffan, 2019(Laffan, , 2023)), May was forced into a series of climbdowns, resulting in her rolling back on a number of the 'red lines'.May's revealed preference, when eventually forced to acknowledge the trade-offs between continuity and autonomy, was to embrace the former, even as her rhetoric hued closer to the line of the Brexiteers (Brusenbauch Meislova, 2019).
The underlying desire for continuity post-Brexit coupled with a more strident rhetoric can be seen in the government's approach to foreign and security policy.The Lancaster House speech articulated a 'Global Britain' vision that became a much-deployed slogan during the May era (Daddow, 2019;Gamble, 2021;Turner, 2019), echoing the Leave campaign's preoccupation with Britain resuming its global role post-Brexit (Rogstad & Martill, 2022).Yet observers noted the concept had little substance (Turner, 2019), was difficult to distinguish from the UK's existing priorities (Haacke & Breen, 2019), and failed to offer a realistic appraisal of Britain's role in the contemporary global order (Blagden, 2019;Hill, 2018).In practice, for all its emphasis on Britain's new global role, the UK's foreign policy priorities under the May government differed little the Cameron era.The Conservative Party manifesto in June 2017 promised Britain would act globally to promote democracy and human rights, contribute to development goals, and prioritise its relationships with the United States, European partners and other global actors (Conservative Party, 2017).On the pressing foreign policy questions of the day, the UK and its European partners remained in lockstep, with clearly articulated shared positions on the Iran deal (the JCPOA), the Paris climate agreement, and the need for a strong response to the Salisbury poisonings in March 2018 (Whitman, 2019, p. 399).When it came to European security issues, the May government quickly signed up to French President Emmanuel Macron's European Intervention Initiative (EI2) (Sweeney & Winn, 2022) while at the operational levels both sides continued to work together on the assumption that significant continuity would come to mark the relationship even after Brexit (Svendsen & Adler-Nissen, 2019).
In May 2018, the government outlined proposals for a comprehensive agreement on security and defence, envisioning structured cooperation across multiple levelspolitical and strategicon different areas with regularised meetings, alongside the potential for the UK to participate in CSDP missions where appropriate and in projects under the aegis of the recently launched Permanent Structured Cooperation (PESCO).The text, moreover, proposed observer status for the UK in decision-making forums where those decisions concerned operations that would include the UK (HM Government, 2018a).The proposals were more ambitious than existing forms of third country association, proposing structured cooperation across all levels as well as a potential Framework Participation Agreement (FPA) (Interview 13).But there was no intention to build formal institutional structures and the level of institutionalisation remained low, with the FPA the only legally binding aspect (Interviews 9 and 10).While the EU was keen for a security agreement (Interview 8), from London's perspective a deal also made sense, since it was an area where the UK had much to offer an could show it was willing to make a contribution, setting a positive tone for the future partnership (Interview 9).Yet although the idea of a UK commitment to the CFSP/CSDP offered leverage, there was no insinuation that London's security commitment was being traded off for economic advantage, this rather reflecting the desire to ring-fence existing collaborative ties from the negotiations (Interview 9).
While the EU pushed back on some aspects of the proposalsespecially the idea that Britain could shape EU decisions from outside (Interview 5; European Parliament, 2018)the idea of a security agreement was viewed favourably in Brussels (Interview 8).Domestically, however, the proposals came under fire from the pro-Brexit right.Jacob Rees-Mogg, the most outspoken critic of May at the time, and a doyen of the pro-Brexit faction, called for an inquiry when May's security proposals were leaked in March 2018, accusing civil servants of 'a clear attempt to fix the game' and of 'appearing to brief against their country' (The Express, 2018).Peter Lyon, writing for the pro-Brexit news website Brexit Central, founded by the former Vote Leave strategist Matthew Elliot, claimed the ''deep and special partnership' with the EU constitutes a clear threat to UK defence autonomy' (Lyon, 2018).Damien Phillips, in the Telegraph, a Conservative-supporting newspaper, argued that May's deal would result in Britain being abused by the EU (Phillips, 2018).Sir Richard Dearlove, former head of MI6, and Charles Guthrie, former Chief of the Defence Staffboth Leave supporterswrote to the chairmen of the local Conservative associations to warn of the partnership 'hidden' in the agreement and the risk to national security it posed, encouraging MPs to 'vote[ ] against this bad agreement and support[ ] a sovereign Brexit on WTO rules' (Reuters, 2019).
Opposition to the security agreement was sufficient neither to alter the prime minister's course nor to scupper her agreement, but it did highlight the pro-Brexit faction's opposition to seeing the UK tied into EU security initiatives.The criticism of May's partnership was part of growing opposition to her Brexit course during 2018, as May's concessions in the negotiations and the growing realisation that her 'red lines' would be fudged caused consternation on the party right (Grey, 2021).For many on the right, May's hard-line rhetoric did not match the reality of her Withdrawal Agreement, or her plans for the future relationshipthe Chequers Proposal (HM Government, 2018b) and her deal was increasingly portrayed as a bad one as a result (Kettell & Kerr, 2020).Since both factions held an effective veto over the government's Brexit policy, a politics of intransigence resulted, with both sides refusing to endorse any compromise solution (Heinkelmann-Wild et al., 2020).May's efforts to force MPs into voting her deal through by threatening each side with their least favourite outcome -'hard' Brexit or 'no Brexit'summarily failed, as each side came to believe the opposite would happen (Seldon, 2019, p. 447).In the end, May's agreement, with the security proposals in the appended Political Declaration, was defeated on three separate occasions between January and March 2019, fatally undermining May's position.

Autonomy under Boris Johnson
After May resigned, Johnson was elected leader of the Conservative Party, becoming Prime Minister on 24 July 2019.Politically, while Johnson had infamously equivocated over which side to back in the referendum, since his resignation in July 2018 he has become the de facto spokesperson for the Conservative right and for a harder Brexit.Unlike May, who had sought a bespoke model of association for the EU that would allow for continued participation in some EU policies and not others, Johnson aimed to maximise the UK's regulatory autonomy from the EU.Having committed to renegotiate May's Withdrawal Agreement, Johnson's first task upon taking office was to push the European Council to consider amending parts of the deal.In the revised version of the Political Declaration the language on security and defence was altered to emphasise UK sovereignty, but the intention to negotiate an agreement in the talks on the future relationship remained intact.Following the 12 December 2019 general election, in which the Conservatives obtained an 80-seat majority, Johnson was able to comfortably pass the amended Withdrawal Agreement and Political Declaration, with the UK entering the transition period on 1 January 2020.This provided a window for both sides to negotiate the terms of the future relationship, and since Johnson was clear about a more autonomous relationship with Brussels, this would take the form of an FTA (Usherwood, 2021).
When the talks began, one of the first actions of the Johnson government was to announce that these would not cover the proposed security and defence agreement, which was contained in the Political Declaration (Barnier, 2021, p. 316).The decision both surprised and disappointed the Commission, which saw the Political Declaration as a seriousalbeit not legaldocument, which committed both sides to negotiating a security agreement (Grey, 2021, p. 210).For the Johnson government, the removal of security issues from the negotiations fitted with its overall view of Brexit, since it was one area where the re-gaining of sovereignty could be demonstrated in a highly visible manner, and was thus of value symbolically (Interview 9).Moreover, with the economic relationship now intended to be a more distant one, there was felt to be less need forand a lower level of benefit froma closer political relationship (Interview 9).The absence of an EU-level agreement was also part-and-parcel of London's alternative approach, which was to prioritise bilateral agreements with European states and to find alternative forums to discuss foreign and security policy issues (Interview 13).The decision was met with regret in Brussels, which had been very keen to obtain a security agreement (Interview 7) -'the only really big thing missing from the EU side' (Interview 8)and was seen as a missed opportunity to signal continuity in underlying political values (Interview 6).While some in Brussels attributed the British decision to London's embrace of a more autonomous Brexit (Interviews 7 and 12), others saw it as a show of strength prior to the negotiations beginning proper (e.g., Barnier, 2021, p. 316;Cloos, 2021).
The foreign policy priorities of the Johnson government also became clearer during 2020, with several developments taking place alongside the negotiations.In June 2020, during the TCA negotiations, Johnson announced a merger of the FCO and the Department for International Development (DFID) into the Foreign Commonwealth and Development Office (FCDO), a move long advocated by the party right in order to place greater political control over the development budget.Indeed, both the right-wing Henry Jackson Society and Dominic Cummings, the former Vote Leave Director, had previously proposed such a merger as way to channel foreign aid towards would-be post-Brexit trading partners (The Independent, 2019).In July 2020, Foreign Secretary Raab announced cuts of £2.9bn to the UK's overseas aid budget, temporarily curtailing the UK's commitment to spend 0.7 per cent of GDP on development, a move which was again popular among the Conservative right, but which critics argued would dent the UK's soft power (The Guardian, 2021).The immediate rationale for the reduction in aid spending came from the dismal fiscal situation brought about by the Covid pandemic, but this did not detract from the fact it appeased those on the party right who believed the UK paid too much overseas.
The end of the transition period in December 2020 severed Britain's access to the CFSP/CSDP and left the UK without a formal means of discerning the EU position and without an avenue for structured coordination with the EU27 (Interview 10).Moreover, the UK government's refusal to implement the border checks required by the Northern Ireland Protocol soured political relations and undermined the willingness of either side to engage constructively in other areas (Interview 13).In a bizarre reversal of roles, the UK has found itself at times dependent on the US as an interlocutor for the Europeans, given the absence of direct UK-EU ties (Interview 16).Meetings with counterparts between the UK and the EU foreign ministries were made more difficult by the political situation, with political masters on both sides more sceptical of endorsing informal contacts (Interview 13).And yet the severing of the institutional ties was cushioned by the institutional knowledge and informal contacts those working on behalf of the UK had amassed over the years of membership (Interview 13).Under Foreign Secretary Dominic Raab, Britain sought an 'ad hoc' approach to European security cooperation which sought to utilise existing channels and strengthen bilateral relationships (Cladi, 2021;House of Commons, 2021).In March 2021, the UK signed a Statement of Intent with Estonia, with agreements and declarations following with Belgium, Denmark, Germany, Greece and Latvia (von Ondarza, 2022).Other pre-existing relationships were upgraded, with joint Anglo-Dutch exercises taking place in the Mediterranean in September 2020 (House of Lords, 2021) and proposals (preinvasion) to extend existing security guarantees to Poland to Ukraine (Reuters, 2022).
Strategic changes were forthcoming in the government's Integrated Review of March 2021 (HM Government, 2021a) which set out radical changes to the UK's military forces, envisioning (perhaps overly hastily) the obsolescence of conventional conflict in Europe and committing to redirecting UK defence spending towards the nuclear deterrent and away from personnel and battle tanks (HM Government, 2021a, p. 72).The review also recommended bolstering non-traditional capabilities in such areas as cyber weapons and those aimed at disrupting space-based infrastructure (HM Government, 2021a, p. 71).The framing for the document relied heavily on the language of Global Britain and articulated a vision of the UK as an influential state by virtue of its role as a global networker and its membership of key forums, although the report was noticeably silent on the question of EU security, with a single mention that the UK would cooperate with European partners (HM Government, 2021a, p. 6).The language, carefully crafted, was intended to send a clear signal to the EU that it was to be downgraded in UK foreign policy, and was received poorly in Brussels (Interview 10).Arguably the effort to discursively erase the EU's role as a security actor was part of a broader effort by the Johnson government to 'perform' Brexit, alongside such actions as the repackaging of rollover trade agreements into 'victories' for Global Britain (Heron & Siles-Brügge, 2021) and the downgrading of the EU Ambassador's diplomatic status in London (Interview 13).
The UK's alliance priorities and geographical focus also shifted under the Johnson government, with a notable emphasis on the Asia-Pacific (Haacke & Breen, 2019;Vucetic, 2022, p. 261).In February 2020, the UK announced the deployment of a new carrier strike group to the region, pledging enhanced defence cooperation between the UK and Japan (House of Lords, 2021).In June 2020, the UK applied to become a Dialogue Partner of the Association of South East Asian Nations (ASEAN), which was formalised the following year, a major diplomatic win for London (HM Government, 2021b).On 15 September 2021 the UK agreed a trilateral security pact with the United States and Australiathe AUKUS agreementwhich aims to enhance defence-industrial cooperation in the Asia-Pacific against the (undeclared) threat from China (Whitman, 2021).The arrangement soured Anglo-French relations, with Canberra opting to purchase American submarines as part of the agreement, reneging on an existing deal with France (Vucetic, 2022, p. 261).The diplomatic fallout led to the cancellation of the forthcoming Anglo-French summit and prompted a French approach to Greece with a view to establishing new formats for European defence (Financial Times, 2021).Politically, AUKUS became a keystone in the Global Britain story by emphasising Britain's role as a global actor and its prioritisation of relations with the English-speaking Commonwealth (Interview 14).Yet the defence-industrial gains would accrue to the US and the strategic gains to Australia, whilst the deal undermined London's relationship with Paris, supposedly now the core defence relationship in Britain's post-Brexit European strategy (Interview 14).

The Ukraine war and beyond
On 24 February 2022, Russian forces invaded Ukraine, following a number of tense months in which mobilisation had taken place on Ukraine's borders by Russian and Belorussian troops.The conflict, which is ongoing, proved to be a watershed moment in European security and defence, marking the return of inter-state war in Europe for the first-time since the Second World War, fostering an uptick in European solidarity, and placing economic and social barriers between Russia and European states (Bunde, 2022, p. 517).The UK response to the Ukraine crisis, as might be expected given its warnings of Russian aggression and unflinching support for NATO, was strong and drew the respect of European partners.Pre-existing forms of institutionalised collaboration with Nordic and Baltic states have been stepped up, while the UK has shored up its military presence in Eastern Europe, allowing these states in turn to increase their provision of military aid to Ukraine (Martill & Sus, 2023).The UK has provided significant military and technical assistance to Ukraine, including the export of heavy weaponry, and has enacted a parallel package of sanctions, carefully coordinated with the EU and other global actors (Interview 13).And the UK extended security guarantees to Sweden and Finland following their announcement that they intended to join NATO in order to preclude a security gap arising during the application process (Martill & Sus, 2023).
The crisis also brought about increased engagement between the UK and the EU, even amidst the backdrop of tensions arising from the Brexit divorce, and an increasing number of ad hoc meetings have been held since February 2022 (Interviews 10 and 13).Liz Truss, then Foreign Secretary, attended an extraordinary meeting of the EU's Foreign Affairs Council on 4 March 2022 alongside US Secretary of State Antony Blinken and Canadian Foreign Minister Mélanie Joly to coordinate on sanctions and assistance to Kyiv (Council of the EU, 2022a) and high-level phone conversations reportedly took place between Truss and HR/VP Josep Borrell (Interview 12).The UK and other transatlantic partners have also been involved in the work of the clearing house cell within the EU Military Staff (EUMS) which has been helping coordinate military equipment sent to Ukraine, while the EU's military assistance mission has been closely coordinated with the UK (Interview 10).Perhaps the closest area of cooperation has been sanctions, on which both sides never stopped cooperating, even during the one-year hiatus during 2021 where engagement in other areas was close to non-existent.Cooperation was such that the sanctions packages are now aligned well and the UK has caught up with Brussels after a somewhat slower initial implementation (Interview 13).
The rapprochement brought about by the Ukraine War is a product both of the severity of the external shock and the realisation on behalf of both the UK and the EU of the significance of one another as protagonists in the conflict.For the EU, the invasion highlighted how comparatively significant and proactive the UK could be as a strategic ally, whilst also lending credence to core elements of the UK's worldview, Britain having frequently warned of the threat from a revanchist Russia, long-championed NATO's role as the primary security and defence actor, and always sought to remain in lockstep with the United States (Interview 14).For the UK, while the conflict highlighted some of the limitations of the EU as a strategic actor, it also made clear how much concerted action could be achieved by 'collective power Europe' (Laffan, 2023).The EU imposed wide-ranging sanctions on Moscow, the scope of which has increased with successive rounds (Interview 13).By July 2022 the EU had allocated €2.5bn to fund the acquisition of military hardware and protective equipment to the Ukrainian military through the re-purposed European Peace Facility (Council of the EU, 2022b) and the Union responded rapidly to Ukraine's application in February 2022 for membership, affording Kiev candidate status on 23 June 2022 (European Council, 2022, p. 4).The Union is also in the process of setting up a training mission in Ukraine (EUMAM) through the CSDP which will last for two years and is designed to complement the existing missions of the member states (and the UK) (Council of the EU, 2022c).
Yet, outside this relative rapprochement, the invasion of Ukraine led to no change in the overarching institutional security relationship between the UK and the EU and little change in the framing of UK foreign policy.Increased cooperation has taken place through bilateral channels and via essentially ad hoc forumshigh level meetings and telephone callsand there were no calls to revisit the idea of a security partnership until as late as March 2023, when the issue was placed back on the agenda.Continuing political difficulties during the period limited engagements between officials on both sides, even when there was a clear willingness to coordinate, as effort was made to avoid any arrangements which looked like 'entangling alliances' (Interview 10).Moreover, British actions continued to be sold domestically both as a veneration of 'Global Britain' and continued to be contrasted with supposed EU inaction, which irked EU policymakers.The UK's perceived desire to engage in 'political grandstanding' ostensibly belittling the EU's efforts in Ukraineproduced particular annoyance (Interview 10) as did the British tendency to downplay or to not mention areas of cooperation which were taking place (e.g., on sanctions) (Interview 13).

Conclusion
While Brexit has brought considerable change to UK foreign and security policy, the pattern of change has not been linear.The British position was characterised initially by continuity as Theresa May sought to keep the UK closely tied to the EU, and later by greater autonomy, as Boris Johnson succeeded May and sought to implement a more distant vision for Brexit and enact in more practical terms the Global Britain vision.Lying beneath this variation is factional politics within the Conservative Party, which addled May's government and thrust Johnson into the premiership.For while Brexit was a product of Conservative in-fighting, the process also shaped and exacerbated factional tensions, bringing about the ascendency of the Brexiteers in July 2019 and a corresponding shift in British foreign and security policy.Even the seismic shock presented to European nations by the Russian invasion of Ukraine in February 2022 was insufficient to prompt a re-think on the UK-EU security relationship, with the response filtered through the ad hoc and largely bilateral post-Brexit status quo.That the high degree of contiguity in strategic interests has not brought both sides together is surprising, and attests to the significant rupture in the political relationship during the Brexit negotiations, the continuing attachment many Conservatives have to Brexit as a political project (Hix et al., 2023), and the importance the EU itself places on many of the outstanding issues from the negotiations.
While the renewed engagement from February 2022 is encouraging, it cannot substitute for a more institutionalised relationship.For one thing, the ad hoc and sporadic nature of this engagement is inefficient, and makes coordinating policies more difficult and more time-consuming (Interview 11).It also prevents the UK from acting as an agenda-setter, leaving 'alignment' with EU actions as the best available option (Interview 13).And it makes it more difficult to demonstrate the kind of solidarity which many Europeans feel is a necessary aspect of the combined, Western response to Putin's aggression (Interview 10).Moreover, while the kind of ad hoc relationship established after Russia's invasion might be suitable for crisis situations, it cannot necessarily be depended on to deal with future contingencies, or non-crisis circumstances which are less conducive to 'punching through' bureaucratic structures (Interview 10).Efforts to shift cooperation into alternative formats also have clear problems.Bilateralism is inefficient, and the pattern of UK bilateral relationships uneven.European Political Cooperation (EPC) offers a potentially useful venue, but it is not geared to security cooperation, and Britain's support for the initiative seems thus far to be dependent on how it is framed in relation to the EU.NATO ties are very important, but as a military alliance NATO does not have recourse to some of the civilian tools which will matter more for post-war reconstruction in Ukraine, and is in some ways too close to the conflict, with a corresponding risk of escalation where NATO acts (Interview 12).
Recent developments in British politics, including Johnson's removal from power, have brought about a thaw in the political relationship.While both Liz Truss and Rishi Sunak cultivated Eurosceptic personas in their appeals to the Conservative membership, in practice they were both more cooperative than the Johnson government.Truss responded positively to Macron's EPC forum, offering to host a meeting (Turner, 2022), and oversaw Britain's accession to the Military Mobility project in PESCO, before her brief premiership was terminated (Interview 12).Her successor, Sunak, was rumoured to have been mulling Swiss-style proposals for the economic relationship at one point (The Sunday Times, 2022), although this was received poorly by the Brexit right and has not brought about any further developments.More concretely, the passage of the Windsor Framework -Sunak's negotiated solution to the Northern Ireland border problemon 23 March 2023 has paved the way for closer talks on security and defence cooperation (Financial Times, 2023).This is not surprising, given many in the EU regarded a solution to the Protocol issues as a necessary precursor to renewed structured engagement (Interviews 13 and 15).
Looking towards the future, much will also depend on which party forms the next government.Labour is significantly ahead in the polls at the time of writing, and Shadow Foreign Secretary David Lammy has announced his intention to negotiate a security agreement with the EU if a Labour government is elected (Labour Party, 2023).Labour are keen to signal their ability to repair the political relationship with the EU, but also wary of being associated with any effort to reverse elements of the Brexit vote, especially among Red Wall voters.Cooperation in foreign and security policy is one area where cooperation can be improved without revisiting the UK's relationship to EU law, and the party's proposals are wrapped in the 'take back control' rhetoric borrowed from the Leave campaign.Whether or not the United Kingdom stays united is another area of considerable future uncertainty, with Brexit having done much to destabilise the status quo in relation to the devolved governments, especially in Scotland (Keating, 2022).An independent Scotland would have significant implications for the UK's nuclear deterrent, its defence expenditure, and for its relationship with Europe, although Nicola Sturgeon's resignation as First Minister has seemingly reduced the prospect of independence in the near future.
In terms of this article's broader contribution, the Brexit example helps us understand the role of factional politics in determining the direction of foreign and security policy.This is important, both in terms of identifying the locus of relevant variation, and for ensuring we do not write off partisanship or ideology on the basis that individual parties endorse divergent positions over time.Understanding factional politics allows us to show how diverse ideological positions on external issues are mediated by intra-party struggles, thereby making greater space for ideology and partisanship in our explanations.The findings from the study also highlight the conditions under which factionalism is likely to be most prevalent.Specifically, factional politics is exacerbated where wedge issues divide parties internally, where governments lack a strong majority, where collaboration with other parties is rendered more difficult, and where issues lend themselves to 'outbidding' by rival factions.Structural factors are important, too, since they establish the bounds of variation for viable foreign and security policies.Where states have more choice externally, as Britain does in its choice of European security formats, factional politics is more likely to be translated into policy.