A remote island in the Indian Ocean housing a secretive joint US military base is now under international scrutiny after a long-running territorial dispute between the UK and Mauritius appears to have come to an end.

The atoll of Diego Garcia — the largest of the Chagos Islands, and a relic of the UK’s colonial past — is home to the US Naval Support Facility Diego Garcia, a military facility that was leased to the US Navy after hundreds of native Chagos Islanders were forcibly expelled from the island nearly 60 years ago.

It has since become a quietly powerful strategic base for America’s post-September 11 war on terror — as well as a rumored CIA black site and a landing strip for extralegal flights that amount to state-sponsored kidnapping.

Diego Garcia is roughly 1,000 miles from the nearest landmass. There are no commercial flights or permitted seacraft to get there. Visitors must have a permit to be on land.

As part of its investigation of a historic court case about the treatment of detained Sri Lankan Tamils who filed asylum claims on the island, BBC journalists were offered a rare permission to enter Diego Garcia, uncovering the scope of its secrecy and the UK’s surreal imprint on an island paradise that few people have even been allowed to witness.

Then, on Thursday, after weeks of negotiations, the UK announced it would cede sovereignty of the Chagos Islands to Mauritius in a deal that will allow the US to keep operating the base there for another century.

UK government lawyers tried to block the BBC from attending a hearing in an asylum case on the island, and the US denied permissions for journalists to attend, citing “risks to the security and effective operation” of the military base, according to the BBC.

BBC journalists were ultimately allowed on the island for five days, but with stringent restrictions — including not reporting what those restrictions are.

According to the BBC, there is a movie theater, a British pub, a nightclub with a bulldog logo, a bowling alley, a museum and attached gift shop, with streets bearing names such as Britannia Way and Churchill Road.

The region has been under British control since 1814, and the Chagos Islands were detached from Mauritius in 1965 to create the British Indian Ocean Territory. In 1966, just two years before Mauritius became independent, the UK agreed to lease the island to the US for 50 years, which was then extended to 2036 in 2016.

Expelled islanders would not be allowed to return.

The latest treaty appears to expand that US military presence through the end of the century.

Enslaved people from Madagascar and Mozambique were brought to the islands under French and British rule. Following the UK’s occupation after its separation from Mauritius, more than 1,000 people were rapidly evicted to make way for the military base. Pets were killed, and Chagossians were rounded up in ships and sent to the Seychelles.

The United Nations has ruled that the UK must begin its “decolonization” of the territory and end its “unlawful” occupation. The UK granted citizenship to some Chagossians in 2002, though Chagossians have fought for years to return to their homes.

The US, meanwhile, has used the island for aircraft headed to Iraq and Afghanistan, and to reload submarines with Tomahawk missiles.

In 2015, the chief of staff for former Secretary of State Colin Powell said that the island was used by the CIA for “nefarious activities” and as a “transit site where people were temporarily housed, let us say, and interrogated from time to time.”

Former US military and White House officials also have alleged that the island was used to imprison people, and human rights groups have reported that ships anchored just offshore in territorial waters were used for interrogations. Khalid Sheikh Mohammed was among rumored detainees on the island.

On Thursday, a joint statement from the UK and Mauritius said that “both 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.”

The agreement still allows the UK to “ensure the continued operation of the base well into the next century” — for at least 99 years.

Decades after the UK’s forced removal of indigenous people from the island, the new treaty “will address wrongs of the past and demonstrate the commitment of both parties to support the welfare of Chagossians,” according to the statement.

But they will not be allowed to return to Diego Garcia.

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

President Joe Biden said in a statement that the agreement demonstrates that “countries can overcome long-standing historical challenges to reach peaceful and mutually beneficial outcomes.”

The Diego Garcia base “plays a vital role in national, regional, and global security,” according to the president.

“It enables the United States to support operations that demonstrate our shared commitment to regional stability, provide rapid response to crises, and counter some of the most challenging security threats we face,” he added. “The agreement secures the effective operation of the joint facility on Diego Garcia into the next century.”

UK-based diaspora group Chagossian Voices said it deplored “the exclusion of the Chagossian community from the negotiations.”

“Chagossians … remain powerless and voiceless in determining our own future and the future of our homeland,” the group said in a statement.