British Prime Minister Andy Burnham has opened the possibility of the United Kingdom eventually rejoining the European Union and holding another membership referendum, eight years after Britain voted to leave in 2016. He outlined options ranging from maintaining the current relationship to joining the EU customs union or single market and ultimately rejoining fully. French President Emmanuel Macron welcomed the shift, while Brussels said London must present concrete proposals, particularly on a youth mobility scheme, before the bloc offers concessions. Analysts told CNBC that rejoining could support the U.K.'s faltering economy but would present significant challenges, and Chatham House expert Sebastien Maillard called full re-entry unrealistic for now.