Prime Minister Keir Starmer and President Emmanuel Macron have agreed a pilot "one in, one out" scheme aimed at curbing small-boat crossings of the English Channel. Under the arrangement, migrants who reach the UK illegally will be detained and returned to France, while Britain will admit an equivalent number of vetted asylum seekers who have remained on French soil. The announcement capped Macron’s three-day state visit to London and marks the first bilateral returns framework since the UK left the European Union. Home Secretary Yvette Cooper said the programme will start within weeks and be expanded "step by step", but confirmed that no fixed quota has been set. French media and UK officials have spoken of an initial ceiling of roughly 50 returns a week—far below the 21,000 people who have crossed so far this year. The plan still requires final legal endorsement from Paris, London and the European Commission. Starmer hailed the deal as a “breakthrough moment” that will undermine people-smuggling gangs, while Macron argued that Brexit had exacerbated the crossings by removing previous EU repatriation mechanisms. Conservative opposition politicians dismissed the initiative as a gimmick, warning that returning a small share of arrivals would do little to deter future attempts and could face legal challenges. Beyond migration, the two leaders issued a joint declaration to deepen coordination of their independent nuclear deterrents and confirmed that a multinational "Coalition of the Willing" supporting Ukraine will establish its first headquarters in Paris before rotating to London. Both initiatives are intended to demonstrate tighter Franco-British security cooperation amid concerns over European defence and the war in Ukraine.