Former residents of the Chagos Islands who were forcibly removed from their homeland more than 40 years ago will take their long legal battle to the UK’s highest court on Monday.



They are going to the supreme court in London to challenge a decision made six years ago by the House of Lords which dashed their hopes of returning home to their native islands in the Indian Ocean.

In October 2008, law lords overturned previous decisions made by the high court and court of appeal allowing islanders and their descendants to go back.

Olivier Bancoult, the Chagossian leader who has been fighting in the courts on behalf of the islanders, now argues that the three-to-two majority ruling in favour of the foreign secretary should be set aside.

A panel of five supreme court justices, led by president Lord Neuberger, will hear that the legal challenge is brought on the grounds of alleged “material non-disclosure” by the foreign secretary relating to a 2002 feasibility study into the resettlement of former inhabitants.

A supreme court summary of the case says that since the 2008 ruling, Bancoult “has subsequently been provided with documents relating to the 2002 feasibility study which he contends were not disclosed in the proceedings in breach of the respondent’s (secretary of state) duty of candour in public law proceedings, and which he alleges would have been highly likely to have affected the outcome of the appeal”.

The summary adds: “The appellant then decided to commission a further expert report on the reliability of the feasibility study. The appellant is applying for an order setting aside the judgment of the House of Lords and, if granted, for permission to rely on fresh evidence at the rehearing of the appeal.”

Families were forced to leave the islands in the 1960s and 1970s to make way for a US air force base on the largest island, Diego Garcia. The last residents of the British colony were removed in May 1973.

Courts later ruled that the Chagossians could return to 65 of the islands, but not Diego Garcia.

In 2004, the government used the royal prerogative to nullify the rulings but this was overturned by the high court and court of appeal.

The government then went to the House of Lords in 2008 to argue that allowing the islanders to return would seriously affect defence and security.

At previous hearings the government has said the decision to expel about 2,000 of the islanders was made on the basis that it was necessary for peace, order and good government.