Updates On the Chagos Archipelago Dispute: The Future of UK Foreign Policy and Mauritian Sovereignty
On the 20th of October, Reform UK leader Nigel Farage made headlines yet again for a confrontation in the House of Commons with Labour Minister Stephen Doughty after Farage accused the Labour government of mishandling national security concerns around the Chagos Islands. Given the sheer volume of media attention Farage manages to generate weekly, even shrewd political observers can be forgiven for overlooking a few. However, this one in particular most likely deserves more attention that it has yet attracted. The subject of the House of Commons dispute was a bill passed that day ratifying a May 2025 agreement between the UK and Mauritius to return sovereignty of the Chagos Islands to the Mauritian government in exchange for a ninety-nine-year contract allowing the UK to lease the largest island, Diego Garcia, for around £101m per year. The deal is the culmination of a multi decade dispute over the islands’ governance. The current agreement is by no means the first choice for either side, but it is still highly consequential for international security, UK foreign policy, and the global movement towards decolonization.
In 1884, the British Empire seized control of Mauritius, a small island to the east of Madagascar in the Indian Ocean. In 1968, after a fifteen-year push for independence from the UK, it became a sovereign state. At the end of the negotiation proceedings, Section 111 of the new constitution of Mauritius defined the country’s territory as encompassing both the main island and several minor ones including the Chagos Archipelago. In practice however, the United Kingdom retained its authority over the Chagos Archipelago as one of the major conditions of the final agreement. The archipelago had been on the radar of the United States since at least 1964 as a site for a potential military base given its strategic location in the Indian Ocean. Consequently, the US treated the UK as somewhat of a proxy in its negotiations with Mauritius, maintaining its demand to gain operational control of Diego Gargia, the largest island in the archipelago and the present-day site of the base.
Unfortunately for Mauritius, the interest of not one but two major powers in its territorial offerings did little to sweeten the deal for its government or people. On the contrary, the final arrangement between the parties to allow the archipelago to become the British Indian Ocean Territory (BIOT) was less of a deal and more of a strong arming. Mauritius received a £3 million payout in 1965 and in 1966, the UK signed an agreement allowing the US to operate on Diego Garcia in exchange for a discount on US manufactured missiles. Nevertheless, there were several moral and legal problems remaining with the chain of custody of the island. The primary issue when it came time to build the base was the fact that there were already more than a thousand people already inhabiting Diego Garcia, mostly working on plantations. Originally one of the key reasons for the US’s interest in this island specifically was the perceived lack of a native population. As it turned out, having no population indigenous to the island did not mean no one lived there at present. Thus, the US began another chapter in its long history of forcibly displacing groups inconvenient to its wider aims. Beginning in 1968, Chagossians (the residents of Diego Garcia) who left the island were barred from returning. This was followed by restrictions on food and medical supplies and finally by the 1970s the previous inhabitants had been fully replaced by about 3,000 American and British military personnel.
Since the original expulsion, Chagossians have made multiple unsuccessful attempts to recover their right to inhabit Diego Garcia. Their prospects for winning a legal challenge against the displacement went down dramatically in 2010 when the British Government created the world’s largest Marine Protected Area (MPA) in the waters surrounding the Chagos Islands with the express purpose of barring the area from being repopulated. Interestingly, the US is exempt from the environmental restrictions associated with the designation. After the establishment of the MPA, Mauritius ramped up its efforts to reclaim Diego Garcia. Since almost immediately after the transfer in 1965, the Mauritian government has argued that it was forced to cede the Chagos Archipelago under duress and on a dubious legal basis. In 2015, the Permanent Court of Arbitration at the Hague determined both that the MPA was invalid and that, by effectively making Mauritian sovereignty dependent on their relinquishing the archipelago in the 1960s, the UK had violated both Mauritius’ territorial integrity and right to self-determination. In the decade following the MPA being declared invalid, both the UN General Assembly and the International Court of Justice (ICJ) have re-affirmed Mauritius’ original assertion that the Chagos Islands are an integral part of its territory and sovereignty over them cannot be severed and re-assigned to a third party.
Despite the UN and ICJ opinions, the general attitude of both American and British leaders continued to amount to the ends justifying the means. Yes, the international pressure was slightly unpleasant, but Diego Garcia’s location had allowed them access to Asia, Africa, and the Middle East and even granted the ability to launch direct attacks against Afghanistan and Iraq in the 2000s. Going into the 2020s, the rise of Chinese power projection across the Indian Ocean provided little incentive to reverse course. However, in 2022 the calculus began to shift. Facing increasing international pressure, the UK reasoned it would be less costly to come to a new agreement with Mauritius than to face a binding judgement against them in international court and risk access to Diego Garcia altogether. That year both parties committed to moving forward with bilateral negotiations. In 2024, a joint statement between the UK and Mauritius acknowledged Mauritian sovereignty over the Chagos archipelago, while agreeing to a ninety nine-year continuation of military operations on Diego Garcia. Despite agreeing on the end goal of Mauritian sovereignty, both sides continued to reject one another’s terms through 2024 before formally signing the new treaty in May 2025. While outside observers praised the agreement as a commitment to rules-based international relations, both sides have continued to suggest they were pressured to cede too much. In the UK, conservatives like Farage maintain that the treaty both costs more than it should and fails to demonstrate strength against Chinese influence in the Indian Ocean. Chagossians argue it violates their right to return to Diego Garcia previously affirmed by the UN and endangers Chagossian heritage. The staying power of the current agreement remains to be seen but since it comes as one of the first bilateral attempts at such an agreement, at the forefront of a renewed effort at decolonization, it will certainly serve as a case study in sovereignty and a shift in diplomatic leverage in the coming years.
