The Tamils stranded on 'secretive' British island in Indian Ocean

A paradise island in the Indian Ocean has become the centre of a complex legal dispute, a battle for control – and a "prison" for stranded migrants.

In 2021, Sri Lankan Tamils fleeing persecution attempted to sail to Canada to claim asylum, when their fishing boat suffered a leak. British navy ships rescued dozens and brought them to Diego Garcia , the largest of the disputed Chagos Islands in the British Indian Ocean Territory (Biot) – long claimed by Mauritius – and site of a secretive military base leased by the UK to the US. The group of 60, including at least 16 children, claim to have been "unlawfully detained" since: the first people to file asylum claims in the Biot.

The territory's Supreme Court was due to rule on the claim last week, but hours before the judge and lawyers got on the US military plane to start their journey, the US cancelled the hearing. Officials said they were "withdrawing its consent" for access to the "heavily restricted" island, with communication seen by the BBC describing the reasons as "confidential" – but that the visit presented "risks to the security and effective operation" of the base.

But parts of the island where access was denied (such as a gym and a swimming pool) were visited by US cheerleaders and celebrity chefs earlier this year. The fact that the Biot Supreme Court has been "prevented from sitting in its own territory on Crown land is an extraordinary affront to the rule of law", said Tessa Gregory, a partner at Leigh Day, the London-based solicitors representing the Tamils.

The dispute over the Chagos Islands

Diego Garcia is the largest of the Chagos Islands, an archipelago about 310 miles south of The Maldives. The Biot is constitutionally separate from the UK, but administered from London.

The UK took the Chagos Islands from its then colony Mauritius in 1965 and evicted the population of more than 1,000 people, to build a military base. It signed an agreement in 1966 to lease the base to the US for 50 years, which has been extended and is now set to expire in 2036. So although Diego Garcia is technically in a British territory, most of the island is under US military control, including the accommodation and transport.

The US has sent planes from Diego Garcia to bomb Afghanistan and Iraq, while two B52 bombers were sent there for training earlier this year. The CIA has also denied allegations that it has been used as a base to interrogate terror suspects after 9/11.

Since Mauritius gained its independence in 1968, it has claimed ownership of the islands. In 2000, the British High Court ruled that the forceful eviction of Chagossians had been illegal, and granted them right of return – to any island except Diego Garcia.

The International Court of Justice ruled in 2019 that the UK's control of the whole territory was "unlawful" and should end. In 2021, a separate UN maritime court found that the UK's control of the islands amounted to an "unlawful occupation".

But "regardless of widespread international opinion in favour of Mauritius, London has largely ignored these decisions", said Foreign Policy . The UK government also argues that the refugee convention does not apply there.

Foreign Office plans to give the Chagos Islands back to Mauritius in a "Cyprus-style deal" were scrapped earlier this year, said The Telegraph . Then defence secretary Grant Shapps "urged" David Cameron not to cede the islands to Mauritius – a growing ally of China.

The plight of migrants on Diego Garcia

"In many ways, the island – with its pure white sands, palm trees and azure seas – looks a lot like paradise", said The Guardian . But for the 60 asylum seekers, "that idyll could not be further from their reality" – they remain "stuck there" in a "desperate, dangerous limbo".

They are forced to live in a "makeshift tented camp the size of a football pitch, surrounded by a 7ft-high metal fence". The tents are "infested with rats, mice and cockroaches". One person told the paper: "My mental state is deteriorating. I live in a body that has no life inside it".

Many of the detainees "say they are escaping torture and persecution by either Sri Lankan security forces" due to their Tamil ethnicity, said The New Humanitarian , or Indian security forces due to being Sri Lankan refugees.

But on Diego Garcia, guarded by private security company G4S, "they are treating us like prisoners", two asylum seekers said in an anonymous written statement. A G4S spokesperson denied the claims, saying the company "treats the migrants on the island with dignity and respect at all times".

But there have been "multiple suicide attempts" and "reports of sexual harassment and assaults", said the BBC. Some have been flown to Rwanda for medical treatment, but remain under Biot administration. "During Tuesday’s virtual hearing, one of the migrants on the island collapsed multiple times."

Last year, UN representatives who visited the camp reported that "conditions there amounted to arbitrary detention". The Foreign Office has also said that the island is not suitable for migrants. A ruling in their favour could allow them to claim compensation for years of detention, as well as having implications for Chagossians' calls for reparations for their eviction.

The asylum seekers are "pinning all their hopes on their legal teams to get them off the island and to a place of safety where their troubled children can thrive", said The Guardian. One told the paper: "We hope we will be allowed to escape from hell."