The UK is fully committed to holding Russia to account for its actions in Ukraine. On 20 January, the Foreign Secretary announced that the UK had accepted an invitation to join a ‘core group’ of States to shape thinking on how to ensure criminal accountability for the crime of aggression allegedly committed in and against Ukraine, including through a special tribunal. This government, alongside its international partners such as the United States, is considering very closely what a new tribunal might look like. The details of the proposal will matter. Any new tribunal will need sufficient international support and must not undermine the existing accountability mechanisms, such as the International Criminal Court.