Prime Minister of the United Kingdom Sir Keir Starmer is welcomed by the president of the European Commission Ursula von der Leyen at the E.U. Commission headquarters on Oct. 2, 2024. —Thierry Monasse—Getty ImagesThe debate over Brexit and whether the United Kingdom could rejoin the European Union has returned to the forefront of British politics at a time of great instability.Former Health Secretary Wes Streeting, who resigned last week citing …