The Russian invasion of Ukraine increased the European Union’s (EU) ambitions in security in defence as well as member states’ appetite for EU-led solutions in this field. Specifically, the war unveiled the role of the European Commission as a policy entrepreneur which is enhancing its competences in security and defence through the usage of a ‘market-security nexus’. As defence cooperation gets increasingly framed by the EU in terms of economic efficiency and resilience, it might be difficult for London to ignore the gravitational pull of EU market and legislation in the long term. However, EU efforts in regulating the defence market are still nascent, and there are still both room and value for the UK to engage in this process. This submission is divided into three sections addressing the Terms of Reference (ToRs) 1, 3 and 5, respectively. Lastly, it concludes with a policy recommendations section suggesting specific avenues for defence cooperation within existing EU frameworks.