Trusting old friends: the evolution of Euro-British intelligence-sharing through Brexit and beyond

This article examines how the foreign intelligence-sharing relationship between the European Union and the United Kingdom adapted firstly to Brexit, then to Russia’s invasion of Ukraine. Through a socio-relational lens, it reveals how mutual trust is crucial in how the parties respond to change. Novel data collected in elite interviews with security practitioners reveals how trust is understood and operationalised differently at the inter-polity, inter-organisational and inter-personal cooperative levels. The results reveal the importance of lower-level trust dynamics, which grant flexibility to the relationship; yet, inter-polity agreements – such as the 2025 Security and Defence Partnership – remain fundamental for long-term stability.