Overview

• Britain and Mauritius signed a May 2025 agreement that returns sovereignty of the Chagos Archipelago to Mauritius while ensuring a 99-year lease for the UK-US military base on Diego Garcia.
• A House of Lords report cautions that failure to ratify the deal could prompt Mauritius to seek an international ruling that jeopardises the UK’s right to operate the base.
• Under the agreement, the UK will pay at least £120 million annually for 99 years, amounting to over £13 billion, and establish a £40 million fund for displaced Chagossians.
• The pact prohibits development on the remainder of the archipelago without UK consent to block potential foreign, notably Chinese, installations.
• Lawmakers warn that renewal beyond the initial 99-year term is not guaranteed and that the base could face future vulnerabilities from China’s expanding military ambitions.