In a landmark diplomatic move, the United Kingdom has formally agreed to transfer sovereignty of the Chagos Islands to Mauritius, concluding decades of international legal dispute. The core of the agreement ensures the UK retains a long-term lease on Diego Garcia, home to a strategically vital joint UK-US military base.
The Path to a Sovereignty Deal
The archipelago, located in the Indian Ocean, has been a British territory since 1814. However, its detachment from Mauritius upon the latter's independence in 1968 sparked a prolonged sovereignty claim. Mauritius pursued this claim through international courts, culminating in a 2019 non-binding ruling from the International Court of Justice (ICJ). The court found that the UK's administration of the islands should end "as rapidly as possible".
Negotiations began under former Prime Minister Rishi Sunak's Conservative government in 2022, with 11 rounds of talks held before the 2024 general election. The Labour government under Sir Keir Starmer finalised the political agreement, which was signed by Starmer and Mauritian Prime Minister Navin Ramgoolam on 22 May 2025. Starmer argued that without a deal, the UK faced imminent legal challenges and the risk of other nations, like China, establishing a presence on the outer islands.
Terms and Political Reaction
The treaty's key provisions are clear: Mauritius assumes sovereignty over the entire Chagos archipelago, while the UK secures an initial 99-year lease for Diego Garcia, with an option to extend. The UK will pay for this lease, with the total finance package estimated at £3.4bn in net present value, averaging about £101m annually.
The deal has ignited fierce political debate. While the US government stated it "secures the long-term, stable, and effective operation" of the base, former US President Donald Trump labelled the UK's plan "an act of great stupidity" in a post on Truth Social. In the UK, Conservative leader Kemi Badenoch criticised the agreement as a "surrender", claiming the UK was "handing over British territory and paying upwards of £30bn" to a country that "openly cuddles up to China and Russia".
Strategic Implications and the Road Ahead
The primary driver for the UK government was securing legal certainty for the future of the Diego Garcia base. Officials argued that continued challenges in international courts posed a significant risk to the facility's long-term viability. The treaty is designed to provide that stability, ensuring the base remains a key asset for Western defence in the Indian Ocean for the next century.
The agreement marks a significant shift in British foreign policy, prioritising adherence to international law and diplomatic resolution over prolonged territorial control. It closes a contentious chapter in the UK's post-colonial history, though the financial cost and political criticism ensure it will remain a topic of discussion in Westminster and beyond for years to come.
