The Chagos Islands

Plantations and a colony

The Chagos Archipelago is a semicircle of atolls about 1,600 km south of the tip of India, out of the path of cyclones. Portuguese explorers found them uninhabited in the 16th century. In the late 18th century France took them as a dependency of Mauritius and set up coconut plantations worked by slaves brought from Africa; Britain took over in the early 19th century, and they passed to it with Mauritius in 1814.^[1]

Split off and emptied

During the Cold War, Britain and the United States agreed to set up defence facilities in the Indian Ocean. In 1965 Britain detached the Chagos from Mauritius, three years before Mauritius became independent, and made it part of a new British Indian Ocean Territory.^[1][2] Mauritius later said it had been forced to give up the islands in exchange for independence.^[1]

Between 1967 and 1973 Britain removed the Ilois, or Chagossians, descendants of African slaves and Indian plantation workers; most were resettled in Mauritius and some in Seychelles and Britain.^[1] A US–UK base was built on Diego Garcia in 1971, and it has supported US operations from Vietnam to Iraq and Afghanistan.^[1][2]

In the courts

In 2000 Britain’s High Court ruled the removals illegal and granted the islanders a right to return to every island except Diego Garcia, but in 2008 the Law Lords ruled against them, though the government expressed regret. A no-fishing marine reserve announced in 2010 was opposed by many Chagossians, who said it would leave them no living if they ever returned.^[1]

At the request of the UN General Assembly, the International Court of Justice gave an advisory opinion in February 2019 that Mauritius’s decolonisation had been unlawful, and that Britain should end its administration of the islands as soon as possible. The opinion was not binding but carried great weight.^[1]

A treaty in limbo

Talks began in 2022, and in May 2025 Britain and Mauritius signed a treaty handing sovereignty to Mauritius, with Britain leasing back Diego Garcia for at least 99 years for at least £120 million a year. Prime Minister Keir Starmer argued that court rulings had cast doubt on Britain’s claim and that only a deal could secure the base.^[2][3]

The Trump administration first welcomed the treaty, but in January 2026 Donald Trump called it “an act of GREAT STUPIDITY”, and the bill to implement it ran out of time when Parliament’s session ended in May.^[2] On 22 September 2026 Trump told Starmer’s successor, Andy Burnham, it was a “terrible deal”, and the defence secretary, Wes Streeting, said Britain would go back to the drawing board and suspend the lease payments for now.^[3]