At a strategic level, the institutional development of the European Union has been directed at providing sufficient democratic foundations to underpin enhanced integration across various policy dimensions, through Treaty reforms, inter-governmental mechanisms such as the European Council and an enhanced role for the directly-elected European Parliament.
However, the Brexit decision now compels Europe to also develop mechanisms to foster collaboration between two entities (the EU and the UK) that will no longer be bound together by a common multi-layered institutional framework. While the trilemma framework is perhaps too stark, it is analytically helpful to recognise the genuine tensions across inter-linked policy dimensions.