UK’s Chagos Islands Handover Sparks Concerns Over Sovereignty and Security

A Union Jack flag in front of the Elizabeth Tower, commonly known as Big Ben, in London on Feb. 1, 2017. Jack Taylor/Getty Images

The UK’s agreement to hand over the Chagos Islands to Mauritius has raised concerns among analysts and politicians about its potential implications for other territorial disputes, including the Falklands and Gibraltar.

The Chagos Islands, a small archipelago in the Indian Ocean also known as the British Indian Ocean Territory (BIOT), is set to be handed over to Mauritius, after years of negotiations.

Under the agreement, signed in October, the British–U.S. naval and bomber base on the largest of the islands, Diego Garcia, would remain under UK control for at least 99 years.

The UK intends to treat the Chagos sovereignty decision as a one-off, with Foreign Secretary David Lammy stressing  that the status of UK’s overseas territories, including the Falklands and Gibraltar, is “not up for negotiation.”

However, according to foreign policy analysts, the decision to cede the archipelago will have “impacts elsewhere,” potentially including Britain’s remaining overseas territories.

Hillary Briffa, assistant director of the Centre for Defence Studies at King’s College London, acknowledged Britain’s success in securing a 99-year lease on the Diego Garcia base but cautioned that the Chagos deal could trigger international calls for decolonisation and debate over the precedent it establishes.

This includes implications for UK allies, from France to Australia, she added.

Similarly, Samir Puri from Chatham House has warned the deal could set a precedent affecting UK territories like the RAF bases in Cyprus, which remained British after Cyprus’s independence in 1960.

Falklands and Gibraltar Under Scrutiny

The UK defends its sovereignty over the Falklands and Gibraltar through self-determination.

Argentina still claims the territory, despite a 2013 referendum where 99.8 percent of Falkland Islanders voted to remain British, Argentina still claims the territory.

Similarly, Spain continues to dispute Gibraltar’s status, though its residents have repeatedly voted to stay under UK control.

In October, the then Foreign Minister of Argentina, Diana Mondino, welcomed the Chagos Islands agreement and said it was a “step in the right direction and the end to outdated practices.”

“With concrete actions and not empty rhetoric, we will recover full sovereignty over our Malvinas Islands. The Malvinas were, are and will always be Argentine,” she said.

The former Secretary of Defence under the Conservative government, Sir Michael Fallon has suggested in his comments to The Telegraph that ceding Chagos Islands “cast Gibraltar’s future in doubt” and “played directly into Spain’s hands.”

“Surrendering the Chagos for fear of a potential international judgement will only encourage Spain to build up international support for its claim. That just means open season for any of these potential claims to be advanced,” he said.

However, according to Lammy, the Chief Minister of Gibraltar Fabian Picardo backed the agreement and said there is “no possible read across” to Gibraltar on the issue of sovereignty.

Similarly, Lammy added, the Governor of the Falklands Alison Blake confirmed that the historic contexts of the Chagos Archipelago and Falklands are “very different.”

Diego Garcia, the largest island in the Chagos Archipelago and site of a major United States military base in the middle of the Indian Ocean leased from Britain in 1966. File Photo

Self-Determination

The Chagos Archipelago was once home to 2,000 Ilois workers, expelled in the 1960s to Mauritius and the Seychelles.

In 2019, the ICJ ruled the UK’s claim to the islands unlawful and called for their return to Mauritius, highlighting the UK’s colonial legacy.

The decision followed a UN referral initiated by Mauritius in 2017, marking a diplomatic setback for the UK amid Brexit tensions.

While the legal circumstances differ—for example, the Falklands’ claim hinges on issues of settlement and self-determination, whereas Chagos involves the unlawful detachment of land—the broader principle of resolving territorial disputes through international consensus could gain traction.

Carl Patrick Stephen Hunter from the Council on Geostrategy noted that while self-determination is a guiding principle in British policy, it was “not applied” in the British Indian Ocean Territory settlement.

“It would mean far more to the islanders, given their unfortunate expulsions, if it were today,” he said, adding that the inconsistency could undermine the UK’s position in defending self-determination in other territories.

A joint statement by the governments of UK and Mauritius said that the new deal will “address wrongs of the past” and support the welfare of Chagossians.”

However, analysts have raised concerns about Mauritius gaining sovereignty over the Chagos Islands, pointing to its poor treatment of the displaced Chagossians.

David Blagden, associate professor of International Security and Strategy at the University of Exeter, said that Britain’s “heinous” treatment of the Chagossian people doesn’t mean that Mauritius “which illiberally [sic] outlawed dissent over their status,” should be granted sovereignty instead.

Associate fellow at the Council on Geostrategy, Paul Mason, agreed that Chagossians should have been more actively consulted, but said the deal is unlikely to create a precedent.

US, China, and Strategic Risks

Labour has confirmed that Donald Trump’s administration will be consulted before the deal, which is not expected to be signed before Monday, is finalised.

The president-elect’s pick for secretary of state, Marco Rubio, has previously warned that the deal poses a “serious threat” to U.S. national security by transferring the islands to a nation allied with China.

Rejecting claims that Britain handed over the Chagos Islands to an ally of China, UK negotiator Jonathan Powell said that the deal was reached in close consultation with U.S. officials.

Puri noted concerns that China could use the decision as an opportunity to develop commercial ports in the region and compete with India for economic and strategic influence. However, he added, this is a long-term issue to monitor, independent of the UK’s decision on Chagos.

The UK has bolstered its engagement in the Indo-Pacific through several key partnerships, including the AUKUS Security Partnership and free trade deals with Australia and New Zealand.

Euan Graham, senior analyst at the Australian Strategic Policy Institute, has suggested that finalising the deal quickly could help the UK minimise political risks.

“The BIOT has unfortunately become a net liability to the UK, and the dispute with Mauritius, an irksome distraction from the positive Indo-Pacific partnerships which the UK has established,” he said.

Sam Goodman from the China Strategic Risks Institute said Beijing likely views the deal as proof of the UK’s decline as a “middle power,” with little influence in the Indo-Pacific and heavily reliant on US policies, especially through the Diego Garcia base.

“What remains to be seen is how this decision fits with the illusive vision of what the UK’s purpose should be in an increasingly geopolitically unstable world,” he added.

A Mauritius delegation is expected to continue negotiations after the Mauritian Cabinet withheld approval of the agreement.

Once finalised, the handover will mark the first time the UK has ceded territory since Hong Kong in 1997.