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British Sovereignty Protection (Chagos Islands) Bill [HL]: HL Bill 15 of 2026–27

Approximate read time: 20 minutes

The Chagos Archipelago is a group of islands which make up the British Indian Ocean Territory (BIOT). It was created in 1965, when the UK separated the archipelago from Mauritius ahead of the latter’s independence in 1968. The largest of the islands, Diego Garcia, became a joint UK-US military base following the removal of between 1,400 and 1,700 Chagossians.

Mauritius has contested the UK’s sovereignty. In 2019, the International Court of Justice issued an advisory opinion stating the UK should transfer sovereignty of the islands to Mauritius, with the United Nations General Assembly voting to welcome the advisory opinion.

In response, the UK government signed an agreement in 2025 which would recognise Mauritius as sovereign over the islands, including Diego Garcia, but also authorise the UK to use Diego Garcia for military purposes for an initial 99-year period at an estimated cost of £3.4bn. The government laid its agreement before Parliament and introduced a bill to implement the accord in domestic law. However, due to a change in the US president’s position, the agreement was effectively paused and the bill fell at the end of the 2024–26 parliamentary session. In September 2026, the UK government said the agreement would be reviewed.

The British Sovereignty Protection (Chagos Islands) Bill [HL] is due to be debated at second reading in the House of Lords on 23 October 2026.

Image from Wikimedia Commons.