The Chagos Islands deal, explained

Donald Trump has indicated that he would be prepared to back Keir Starmer's deal to hand over sovereignty of the Chagos Islands to Mauritius.

The Labour government has effectively offered the president a veto on the controversial plan, because of its implications for US security. The agreement would allow the UK to continue to lease one of the islands, Diego Garcia, the site of a strategically crucial UK-US military airbase. But some in the Republican camp have argued that the plan could end up benefitting China, because of its close links with Mauritius.

The US administration has "got to be happy with the deal", David Lammy told ITV's "Peston", "or there is no deal".

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Why are the islands British anyway?

The Chagos Islands, an archipelago of 58 islands in the Indian Ocean about halfway between Tanzania and Indonesia, were given to Britain by France in 1814 during the Napoleonic Wars. France ceded control of Mauritius and its dependencies, including the islands, which were valued for their coconut plantations and their position on trade routes between Africa and Asia.

In 1965, shortly before granting Mauritius independence, Britain separated the Chagos Islands, renaming them the British Indian Ocean Territory, and paying £3 million to Mauritius. The following year, Harold Wilson's government leased the largest island, Diego Garcia, to the US for use as a military base in exchange for a discount on Polaris nuclear missiles.

How did the agreement affect the Chagos islanders?

It required the expulsion of up to 2,000 or so Chagossians, French Creole speakers also known as the Illois – descendants of African slaves brought to work on the plantations. The British authorities, who described the islanders as "some few Tarzans or Man Fridays whose origins are obscure", drove them out by closing down the coconut plantations and, eventually, deporting the remaining residents to Mauritius and the Seychelles in the early 1970s. Many were left in the slums of the Mauritian capital of Port Louis, where suicides and addiction were common.

A long-running campaign by the Chagossians eventually led to the UK granting them £4 million in compensation in 1982, on condition that they renounced all rights to return home. Following further legal battles, in recognition of injustices they had faced, the islanders and their descendants were offered UK citizenship; many came from Mauritius to live in Crawley, near Gatwick, where they arrived.

How did Mauritius react to all this?

Mauritius has long claimed sovereignty over the Chagos Islands. It took the UK to the UN's International Court of Justice, which in 2019 found that the separation of islands from Mauritius was unlawful, and that the UK's continuing rule would be a "wrongful act".

This was only an "advisory" judgment, not a binding one, which the UK could have ignored, but it was politically damaging. In the same year, the UN General Assembly voted by 116-6 to condemn Britain's occupation of the islands, calling for it to end "as rapidly as possible". Only the US, Israel and a few others voted in support of the UK; even close Nato allies abstained. As a result, Britain entered into negotiations with Mauritius's government.

How might this affect the US?

The US had sought out the Chagos Islands as a military base during the Cold War. At the time, Diego Garcia was the only US base between the Mediterranean and the Philippines. Today, it is still regarded as vital strategically.

The prospect of Mauritian ownership is regarded with suspicion by many in the US, not least because Mauritius has close economic links to China. This posed a diplomatic conundrum for Britain.

How did Britain try to solve it?

Under the draft treaty agreed between Mauritius and the UK last October, Britain would cede sovereignty of the islands to Mauritius, but would also pay the Mauritian government to lease Diego Garcia: the rate is reported to be £90 million a year for at least 99 years, totalling at least £9 billion. Mauritius has agreed not to lease any of the other islands to rival powers.

It was thought, by the Labour government and by UK officials, to be a satisfactory solution: righting historical wrongs and making sure that Britain complied with its legal obligations, but also safeguarding the military base for the foreseeable future. It was welcomed by the Biden administration, as well as by India, the dominant regional power; China did not object to it.

What went wrong?

The politics changed. Mauritius elected a new PM, Navin Ramgoolam, who demanded a chance to renegotiate: having previously called the deal "high treason", he asked for bigger up-front payments from the UK.

President Trump is also thought likely to be highly critical: his secretary of state, Marco Rubio, has argued that it "poses a serious threat to our national security interests in the Indian Ocean and threatens critical US military posture in the region".

Negotiations have now been paused to allow the Trump administration its say. Meanwhile, the agreement with Mauritius has also been much criticised in the UK.

Why has it been criticised in Britain?

First, because of the cost. Reform UK's Nigel Farage asked how Keir Starmer could justify the UK being "prepared to give away a military base and pay £18 billion for the privilege" (the government disputes that figure).

The Tories, who began negotiations when in power, are now strongly against it. "He's freezing pensioners, while shovelling money to Mauritius," complained Kemi Badenoch. Secondly, it is regarded by many as a betrayal of the Chagossians.

How is it a betrayal?

The Chagossians, now some 10,000 strong, have been given practically no voice in the negotiations. Some Mauritian Chagossians, such as the activist Olivier Bancoult, are in favour of the deal. But the 3,500 in Crawley are, according to their MP Peter Lamb, near-universally opposed. They see Mauritius as a distant and hostile power, which treated exiles badly, withholding compensation paid by the UK for them. And there is no guarantee that British Chagossians would be able to return to the islands, although Mauritians without roots there would, it seems, be able to.

The activist Jemmy Simon, whose grandmother was expelled, argues that "it's not right for Mauritius to get sovereignty over the islands without us getting a say". She represents Chagossians who want a referendum to decide ownership.

Diego Garcia: strategic asset

At the height of the Cold War, the US decided that it needed a strategic outpost in the Indian Ocean. Diego Garcia, a tropical atoll in the dead centre of the ocean and far from any threat, was ideal. Construction began in 1971. Today, Naval Support Facility Diego Garcia has an anchorage, an airstrip, and radar and communications facilities. It is home to about 2,400 people, mostly Department of Defence civilians. The roughly 400 US servicemen, and 40-odd members of the British Forces who "maintain sovereignty", see it as a plum posting, with its beaches and clear waters.

Diego Garcia's location allows for deployment of air and naval forces across the Middle East, East Africa and South Asia. It also provides a key refuelling and supply station. It is within striking distance of key maritime chokepoints, such as the Strait of Hormuz and the Strait of Malacca. US bombers from Diego Garcia played a major role in both Iraq wars and the war in Afghanistan in 2001; during the war on terror, it was a "black site" where Al Qaeda suspects were interrogated. It is known that China would like to establish a military facility in the central Indian Ocean; there are fears that it could build a spying hub on another Chagos island under Mauritian rule.