The United Kingdom and France on Tuesday ratified their “one in, one out” migrant returns treaty, bringing it into force immediately. The agreement allows Britain to send back to France some people who arrive on small boats across the English Channel while accepting an equal number of vetted asylum seekers from France who have not attempted the crossing. Home Secretary Yvette Cooper said detentions of new arrivals will begin "within days." Although London has not set a public target, government officials have briefed that the pilot will start with roughly 50 returns a week—about 2,600 a year—and run until June 2026. The European Commission and key EU member states have signed off on the arrangement, which both governments say is designed to undermine people-smuggling gangs. The treaty comes as Britain faces record pressure at its southern coast: more than 25,000 people have reached the UK in small boats so far this year, a 49 % increase on the same period in 2024. Prime Minister Keir Starmer has also earmarked £100 million to hire 300 National Crime Agency officers and expand other border-security measures aimed at curbing the crossings. Critics argue the scale of returns will barely dent overall flows, while advocacy groups in northern France question whether the plan complies with international refugee protections. The Conservative opposition in Westminster says the scheme is less robust than the previous government’s stalled Rwanda deportation policy, underscoring the political stakes as the pilot gets under way.