The UK government has signed a landmark agreement to transfer sovereignty of the Chagos Islands to Mauritius.
At the same time, it secured a long-term lease that allows the US to continue operating a key military base on Diego Garcia, the largest island in the Indian Ocean archipelago.
Under the deal, the UK will pay Mauritius an average of £101 million ($136 million USD) annually to lease the base for at least 99 years.
British Prime Minister, Keir Starmer called the base “crucial” to national security.
“By agreeing to this deal now on our terms, we’re securing strong protections, including from malign influence, that will allow the base to operate well into the next century, helping to keep us safe for generations to come,” he said at a military headquarters in Northwood, near London.
The base has supported US military operations from Vietnam to Iraq and Afghanistan.
It accommodates nuclear submarines, aircraft carriers, and large aircraft used in intelligence gathering.
The deal has been sharply criticized by opposition politicians.
“We should not be paying to surrender British territory to Mauritius,” said Kemi Badenoch, leader of the Conservative Party.
The agreement has also drawn protests from Chagossians — islanders who were forcibly removed in the 1960s and 1970s to make way for the base.
Two campaigners, Bernadette Dugasse and Bertrice Pompe, brought a last-minute legal challenge that temporarily blocked the signing.
The injunction was later lifted by another judge, allowing the deal to go ahead.
Pompe said the outcome was devastating. “A very sad day,” she said. “The rights we are asking for now, we have been fighting for for 60 years. Mauritius is not going to give that to us.”
The agreement includes a trust fund for the Chagossian community and allows Mauritius to begin a resettlement program — but not on Diego Garcia.
There is no legal obligation for displaced residents to be allowed to return.
The UK has controlled the Chagos Islands since 1814. It split them from Mauritius in 1965, three years before Mauritius gained independence.
In 2019, the International Court of Justice issued a non-binding opinion that Britain’s separation of the islands was unlawful.
Starmer said the UK had no legal path to stop the transfer.
“We had to act now because the base was under threat,” he said.
He added that a legal challenge by Mauritius was imminent and the UK had no “realistic prospect of success” in court.
The UK Ministry of Defence said the deal includes several security safeguards.
These include a 24-mile (39 km) exclusion zone around Diego Garcia, a UK veto over development on the other islands, and a ban on foreign military forces elsewhere in the archipelago.
Talks on the deal began in 2022 under the previous Conservative government. Negotiations resumed after Labour came to power in July 2024.
A draft agreement was reached in October, but delays followed due to political changes in Mauritius and disagreements over financial terms.
The UK also paused to consult the U.S. after its own change of government. The Biden administration reviewed the deal, and the new U.S. leadership signed off earlier this year.
U.S. Secretary of State Marco Rubio praised the final outcome.
He said it “secures the long-term, stable, and effective operation of the Diego Garcia base, a critical asset for regional and global security.”
