The UK, which currently administers the islands as the British Indian Ocean Territory (BIOT), expelled the local Chagossian population in the 1960s and 1970s to make way for a joint UK-US military base.

Historic documents show British officials disparaged the local population of at least 1,000 people as “some few Tarzans or Men Fridays” and massacred their pets during the mass deportation.

The International Court of Justice (ICJ) and the International Tribunal for the Law of the Sea (ITLS) have already ruled that the islands belong to Mauritius, having been illegally separated from the rest of the island country during the process of decolonisation.

The UK government yesterday announced that it will recognise Mauritian sovereignty over the Chagos Islands as part of a deal which will allow the military base to remain on Diego Garcia for at least 99 years.

Mauritius will not be able to resettle Chagossians on Diego Garcia – the largest of the seven Chagos Islands – but will be able to start resettling them on the other islands.

In a joint statement, the UK and Mauritian governments said: “Today’s political agreement is subject to the finalisation of a treaty and supporting legal instruments, which both sides have committed to complete as quickly as possible.

“Under the terms of this treaty the United Kingdom will agree that Mauritius is sovereign over the Chagos Archipelago, including Diego Garcia.

“At the same time, both our countries are committed to the need, and will agree in the treaty, to ensure the long-term, secure and effective operation of the existing base on Diego Garcia which plays a vital role in regional and global security.

“For an initial period of 99 years, the United Kingdom will be authorised to exercise with respect to Diego Garcia the sovereign rights and authorities of Mauritius required to ensure the continued operation of the base well into the next century.”

They added: “The treaty will address wrongs of the past and demonstrate the commitment of both parties to support the welfare of Chagossians.

“Mauritius will now be free to implement a programme of resettlement on the islands of the Chagos Archipelago, other than Diego Garcia, and the UK will capitalise a new trust fund, as well as separately provide other support, for the benefit of Chagossians.”