The agreement follows 13 rounds of talks that began in 2022 after Mauritian calls for sovereignty were recognised by the International Court of Justice (ICJ) and the UN General Assembly in 2019 and 2021.

The world court, as the ICJ is known, is the principle judicial organ of the UN which adjudicates disputes between nations.

Before granting independence to Mauritius in 1968, Britain was found to have unlawfully separated it to form a new colony on the Chagos archipelago named the British Indian Ocean Territory (BIOT).

The UK had initially dismissed UN rulings and court judgements demanding it return the islands to Mauritius, arguing that the ICJ ruling was merely an advisory opinion.

Forced displacement of islanders

In splitting the islands from Mauritius, the UK expelled between 1,500 and 2,000 islanders so that it could lease Diego Garcia, the largest of the Chagos islands, to the United States for military use which the two allies have since operated jointly.

According to news reports, the UK falsely declared that Chagos had no permanent population so that it would not have to report its colonial rule to the UN. In reality, the Chagossian community had lived on Chagos for centuries.

The UK and US governments forcibly displaced the Chagossian population between 1967 and 1973 not only reportedly on Diego Garcia, but also Peros Banhos and Salomon.

The campaign challenging British ownership of the Chagos archipelago included the Mauritian ambassador to the UN, Jagdish Koonjul, raising his country’s flag above the atoll of Peros Banhos in a ceremony in February 2022 to mark the first time Mauritius had led an expedition to the territory since the expulsions.

The new agreement

Under Thursday’s agreement, the UK will still retain control of the UK-US military base on Diego Garcia.

The UK Foreign Secretary, David Lammy, said the UK government had secured the future of the military base “as well as guaranteeing our long-term relationship with Mauritius, a close Commonwealth partner”.

However, many Chagossians are still frustrated by the UK government’s lack of consultation with them before Thursday’s announcement, according to news reports.

Chagossian Voices, a community organisation for Chagossians based in the UK and several other countries where islanders have settled, deplored “the exclusion of the Chagossian community from the negotiations”, leaving them “powerless and voiceless in determining our own future and the future of our homeland”.

“The view of Chagossians, the Indigenous inhabitants of the islands, have been consistently and deliberately ignored and we demand full inclusion in the drafting of the treaty,” they added.