Chagos Islands | Deal in deep water

In a social media post, US President Donald Trump urged the UK to “not give up Diego Garcia”, referring to the location of a US-UK military base in the Chagos archipelago.

The UK agreement on the Chagos island group was the result of long negotiations around the archipelago, located in the central Indian Ocean, about 1,600 km off the tip of the Indian subcontinent. The archipelago lies about 2,000 km northeast of Mauritius, midway between East Africa and Indonesia, a UK overseas territory, one of 14 remaining post-colonial territories.

Officially referred to as the British Indian Ocean Territory (BIOT), the group consists of 60 islands in seven ring-shaped coral atolls. The largest, Diego Garcia, hosts a joint US-UK military base that includes an airfield, a deep-water port, and communications and surveillance-related infrastructure. The islands have an American and British military presence and contract civilian personnel but do not host a permanent civilian population today.

The islands were uninhabited when they were discovered by Portuguese explorers in the 16th century. Due to its strategic location on international trade routes, many foreign powers attempted to establish control over the archipelago. In the late 18th century, France annexed the islands along with the Seychelles, treating them as dependencies of Mauritius. In the early 19th century, the islands were annexed by the UK; Mauritius and its dependencies were declared colonies of Britain in 1814 under the Treaty of Paris. Seychelles was separated from Mauritius and became a separate colony in 1903. BIOT came into being in 1965 following the US-UK agreement.

Mauritius gained independence in 1968; The UK paid a £3 million grant to the Chagos Islands to maintain control. In 1971, a military facility was built in Diego García and the local Elois/Chagossians, descended from African slaves and Indian plantation workers, chose to relocate to the Seychelles or Mauritius. Most were resettled in Mauritius, while some went to the UK

Right of return

In 2000, the British High Court ruled that the removal of the Chagossians was illegal and granted them the right to return. It was upheld by the Court of Appeal in 2007 and rejected by the House of Lords in 2008. In 2019 the ICJ issued an advisory ruling that the decolonization process for Mauritius was illegal and recommended that the UK cease administration of the Chagos Islands.

Although non-binding, the ruling carried international weight and the UK government began negotiations on it in 2022 under then-Conservative Prime Minister Rishi Sunak. An agreement was drawn up in October 2024. In May 2025 Labor Prime Minister Keir Starmer and Mauritius Prime Minister Naveen Ramgoolam signed an agreement to transfer sovereignty over the islands to Mauritius. Before the agreement can enter into force, it must be ratified by law, and draft legislation on it is progressing through Parliament.

The plan, estimated to cost £3.4 billion, envisages the UK handing over the Chagos Islands to Mauritius and leasing the military base at Diego Garcia for 99 years at an average of £101 million a year. The agreement includes a £40 million trust fund to support Chagossians who will be allowed to resettle on all islands except Diego Garcia.

Mr. Trump called the deal “an act of great folly” and the loss of land “a threat to our greatest ally.” Describing the island as “strategic”, Mr. Trump suggested Diego Garcia might be brought in to “eliminate a potential attack by a highly unstable and dangerous regime”—a reference to Iran. He also linked the deal with his own designs to buy Greenland.

The UK says the deal is vital to the UK’s security interests, Mr. Starmer said. On the other hand, the deal invited criticism from the Conservatives and Reform UK, who view Mauritius’ relations with China with suspicion.