Former residents of the Chagos Islands who were forcibly removed from their homeland more than 40 years ago have lost their legal challenge to return. (The World needs to know why this small island nation is relevant to Western Security)

Former residents of the Chagos Islands who were forcibly removed from their homeland more than 40 years ago have lost their legal challenge to return.  (The World needs to know why this small island nation is relevant to Western Security)

Families left the Indian Ocean islands in the 1960s and 70s to make way for a US Air Force base on Diego Garcia, the largest of the group of islands.

An Immigration Order preventing anyone from going back was issued in 1971.

The Supreme Court - UK's highest court - upheld a 2008 House of Lords ruling that the exiles could not return.

On 31 August 1903 the Chagos Archipelago was administratively separated from the Seychelles and attached to Mauritius.

In November 1965, the UK purchased the entire Chagos Archipelago from the then self-governing colony of Mauritius for £3 million to create the British Indian Ocean Territory (BIOT), with the intent of ultimately closing the plantations to provide the British territory from which the US would conduct its military activities in the region. On 30 December 1966, the US and the UK executed an Agreement through an Exchange of Notes which permit the United States Armed Forces to use any island of the BIOT for defence purposes for 50 years (until December 2016), followed by a 20-year optional extension (to 2036) to which both parties must agree by December 2014. As of 2010^[update], only the atoll of Diego Garcia has been transformed into a military facility.

Olivier Bancoult, the Chagossian leader who has been fighting in the courts on behalf of the islanders, had argued that decision should be set aside.

In the latest challenge, justices were told it relied heavily on a 2002 feasibility study into resettlement, which concluded that the costs of long-term inhabitation of the outer islands would be prohibitive and life there precarious.

Information about the feasibility study was not disclosed before the decision was made, the islanders said.

But the five justices dismissed the islanders' appeal by a majority of three to two - the same numerical split as the Law Lords in 2008.

Sabrina Jean from Crawley, West Sussex, chairs the Chagos Refugees UK group. Her father was originally from Chagos Island and is one of the 3,000-strong Chagossian community who live in the town, which is near Gatwick Airport.

She told BBC Sussex: "We are disappointed about the result but we will never give up. We will continue our fight to find justice for the Chagossian community. All the people have the right to live on the islands."

The Supreme Court case was the latest in a long legal battle over the right of the islanders to return.

In 2000, High Court judges ruled that Chagossians could return to 65 of the islands, but not to Diego Garcia.

In 2004, the government used the royal prerogative - exercised by ministers in the Queen's name - to effectively nullify the decision.

Then in 2007, the court overturned that order and rejected the government's argument that the royal prerogative was immune from scrutiny.

However, the following year the government won an appeal, with the House of Lords ruling the exiles could not return.