In early April, Finland became the newest member of NATO, significantly changing the Alliance’s northern flank, as well as deeply impacting Nordic and Baltic security in the face of the war in Ukraine. The war has rapidly altered Finnish security policy. Almost immediately after the invasion, public support for NATO membership leaped from a steady 25% in favour to around 75%. On 18 May 2022, Finland and Sweden simultaneously submitted their official letters of application, and NATO heads of state and government invited them both to join the Alliance at the Madrid Summit on 29 June. As Finland officially joined the Alliance in April 2023, we examine the impact of this on the European security environment, as well as on the UK as a growing security actor in Northern Europe, and one with strong bilateral ties to Finland. In this episode of the Global Security Briefing, host Neil Melvin sits down with Matti Pesu, Leading Researcher at the Finnish Institute of International Affairs (FIIA), and Ed Arnold, Research Fellow for European Security at RUSI, to discuss how Finland’s security policy is changing and how NATO membership will likely change Finland as a European security actor. How will the UK–Finnish defence and security relationship develop, and where are the priority areas for enhanced cooperation?