Chagos islanders have hailed a "big victory" after a United Nations court found that Britain illegally seized control of their Indian Ocean archipelago for the construction of a US military base 50 years ago.
The International Court of Justice said Britain's acquisition of the islands in the 60s was "wrongful" and that it must "bring to an end its administration of the Chagos Archipelago as rapidly as possible".
Britain evicted about 2000 people from the islands in the sixties and seventies so the United States could build a large airbase on Diego Garcia, the largest of its atolls. They and their descendants have been campaigning for the right to return ever since.
Olivier Bancoult, chairman of the Mauritius-based Chagos Refugees Group, said: "It is a big victory. We have been suffering for many years."
The ruling is advisory and non-binding but carries significant symbolic weight because it came after the UN General Assembly asked for the court's advice on the case.
Britain paid the then self-governing colony of Mauritius £3 million ($5.7m) for the islands in 1965. It combined them with three islands from the Seychelles to create British Indian Ocean Territory.
Three islands were subsequently returned to the Seychelles. But Britain retained the Chagos Archipelago, which had been chosen as the site of a major base for the US navy and air force.
The International Court of Justice found that although Mauritius' Government agreed to the division when it gained independence in 1968, the "detachment was not based on the free and genuine expression of the will of the people concerned".
The court said: "The United Kingdom is under an obligation to bring to an end to its administration of the Chagos Archipelago as rapidly as possible, allowing Mauritius to complete the decolonisation of its territory."
Pravind Jugnauth, the Prime Minister of Mauritius, hailed the ruling as a "historic moment". He added: "Our territorial integrity will now be made complete, and when that occurs, the Chagossians and their descendants will finally be able to return home."
Britain has apologised for the "shameful" way the evictions were carried out but has refused to allow Chagossians to return.
Diego Garcia was an important US base during the Iraq and Afghanistan conflicts, acting as a launch pad for long-range bombers. The US lease lasts until 2036. The US joined Britain in voting against the resolution.