It was on 31 January 2020 that the United Kingdom’s Withdrawal Agreement from the European Union was signed, followed, after difficult negotiations, by an agreement of 30 December 2020 specifying the arrangements for co-operation between the EU and the UK. This Trade and Cooperation Agreement came into force on a permanent basis in May 2021, marking Britain’s official exit. But things are far from being settled (as has been evident in the area of fisheries or Northern Ireland), and the question of future prospects, both for the UK as a country going it alone on the international stage and its relations with the EU, remains largely open, both in trade/economic terms and at the diplomatic level. Derek Martin and Jean-François Drevet attempt to provide some answers to these questions and to cast light on the post-Brexit future on both sides of the Channel. How do relations stand between London and Brussels? Might they remain lastingly ‘acrimonious’? Will the UK withstand the tensions generated by Brexit among the Celtic nations? Can it recover its major international standing? Two scenarios are proposed: the (probably illusory) advent of a ‘Global Britain’ and the ‘return of the prodigal son’ to the EU (though on what conditions?). In either case, the point is to anticipate what the post-Brexit period could lead to in the medium-to-long term, and for both parties — the UK and the EU — to equip themselves with appropriate strategies.