Lost in the vastness of the Indian Ocean, midway between East Africa and the southern tip of Asia, there is a footprint-shaped coral atoll where orange and blue coconut crabs scuttle across pristine white beaches and turtles wallow in the powder-blue lagoon.

Though it is called Diego Garcia, after the 16th-century Portuguese mariner who supposedly discovered it, it was ceded to Britain following the Napoleonic Wars and has belonged to us ever since, proudly flying a palm tree-embossed Union flag and retaining its old-fashioned Post Office pillar-box.

By rights, I ought to be sending this report to you from this remote and beautiful island, but regrettably that isn’t possible.

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Secrets: The tiny island of Diego Garcia - the 'Guantanamo of the east' - has been linked to the U.S's rendition programme

For in 1966 it was leased by Britain to the United States, which has turned it into a vast military base — ‘the Guantanamo of the East’ — and in the 48 years since then, journalists have been banned from going there.

Such is the cloak of secrecy surrounding Diego Garcia that a Time magazine executive once offered ‘a crate of the finest Bordeaux’ to the writer who filed the first despatch carrying the island’s dateline.

Though one landed there very briefly, when the presidential plane on which he was travelling with George W. Bush made a refuelling stop, the wine has not been claimed.

Even the native population, who were forcibly evicted during the late Sixties and early Seventies to make way for the American takeover — a shameful episode to which we’ll return — are allowed to make only one brief, strictly controlled ‘heritage visit’ each year.

Ever eager to demonstrate their openness and commitment to free speech — values enshrined in their constitution — the U.S. still periodically admits reporters and photographers to Guantanamo, even though draconian censorship seriously restricts what they see. But the only publicly available pictures of Diego Garcia are distant aerial shots.

So what are they so desperate to hide on this achingly beautiful outcrop — which the U.S. Navy, seemingly blind to the irony, has renamed ‘The Footprint to Freedom’? It is a question that has acquired fresh urgency with the release last week of the U.S Senate’s bombshell report on the CIA’s use of torture against suspected terrorists.

Given the weight of evidence proving that Diego Garcia was — at the very least — a key staging post in the U.S. rendition and torture programme, it had been widely expected to feature in the dossier, thus exposing Britain’s involvement beyond doubt.

That the island was not mentioned once in almost 500 heavily redacted pages has merely heightened suspicion of an MI6-orchestrated cover-up.

The Blair administration is accused of tacitly allowing detainees to be transferred through the far-flung British overseas territory

It throws the spotlight back on the Blair government, which stands accused of tacitly allowing detainees either to be transferred through this far-flung British overseas territory during the early years of the War on Terror, or to be detained and interrogated there (or both) and covering up our involvement with a farrago of lies and deceit.

The possibility that Britain might have allowed their home to become a secret torture site is deeply distressing to the displaced people of Diego Garcia — the majority of whom have now resettled in the West Sussex town of Crawley, for reasons I shall explain.

‘Our homeland should only be used for good purposes, not as a second Guantanamo Bay with no set of rules or laws like other countries,’ Allen Vincatassin, exiled president of the Chagos Islands, which include Diego Garcia, told me yesterday.

It should indeed. In 2005, the then Foreign Secretary Jack Straw dismissed the notion that we might have been in league with the Americans over rendition — the secret transfer of terrorist prisoners to remote spots for interrogation — as the stuff of ‘conspiracy theories’.

For that to be true, he told the Commons, both he and his U.S. counterpart, Condoleezza Rice, would need to have lied through their teeth.

Two years later, during the dying days of his premiership, Tony Blair also declared himself ‘satisfied’ that the U.S. had never transferred detainees through any British territories. Rather inconveniently, after Blair left office, human rights groups uncovered incontrovertible proof that aircraft linked to the rendition — terrorist prisoner transfer — had indeed landed at Diego Garcia, forcing David Miliband, who had taken over at the Foreign Office, to admit that his predecessors had seriously misled us.

According to Miliband, two planes, each carrying a single detainee, had stopped off there, in 2002. Straw’s mistake, he said, had been down to an ‘administrative error’. And Blair’s? We are still waiting for that one to be explained away. Meanwhile, discomforting new information has continued to emerge, strongly indicating that there is considerably more to concern us than a couple of rogue aircraft.

The former UN expert on torture, Manfred Nowak, for example, claims to have ‘credible evidence’ that detainees were imprisoned in one of more than 650 featureless concrete buildings that have turned the base at Diego Garcia into a maze-like mini-city, with cinemas and restaurants, much like Guantanamo Bay.

And Dick Marty, a Swiss senator who led a Council of Europe investigation into the CIA’s encroachment into European territory and airspace during the War on Terror, says a CIA source told him the British island had been used.

In 2005, then Foreign Secretary Jack Straw (pictured) dismissed notion that UK might have been involved with the secret transfer of detainess to remote spots for interrogation as the stuff of ‘conspiracy theories’

Then there are the stories of the detainees themselves.

Since they were blindfolded and forced to wear sound-proof earmuffs when being flown to the notorious ‘dark sites’ where they were brutally quizzed, they cannot be sure where they were.

But some are now known to have been held below deck on sinister prison ships, and there is mounting evidence that these were anchored somewhere off Diego Garcia.

Evidence has emerged that the so-called ‘American Taliban’ John Walker Lindh — a U.S. Muslim convert captured in Afghanistan in 2001 — was held on the USS Bataan, which has been serviced from the island’s naval base. Also, the USS Stockholm, deployed to Diego Garcia shortly before the War on Terror began, underwent extensive ‘modifications’ in 2004. Did they include a dungeon?

Then there is the disquieting case of Abdelhakim Belhadj, the exiled Libyan dissident who was arrested and handed back to Colonel Gaddafi soon after the dictator’s notorious ‘deal in the desert’ with Blair.

That the island was not mentioned once in almost 500 heavily redacted pages has merely heightened suspicion of an MI6-orchestrated cover-up

Belhadj also believes he may have been tortured on the island, and the embarrassing truth could yet emerge in his long-running civil action against the British government.

Of course, the flight arrival and departure logs kept on Diego Garcia would go a long way to proving all this one way or the other.

Yet the latest excuse trotted out by the Foreign Office is that the key documents, covering the period when the rendition programme was at its height, were badly damaged by water — presumably from rain leaking into the building where they are kept — in June this year.

Smelling a rat, the London-based human rights organisation Reprieve scoured weather reports for that period and found it to have been unusually dry. The group’s legal director, Cori Crider, says the explanation is of ‘the dog ate my homework’ variety.

For both Britain and America, all this could hardly come at a worse time. In 2016, the 50-year lease on Diego Garcia — which the U.S acquired in return for a $13 million discount on the Polaris nuclear missile system they sold to Britain — is due to expire.

But the deal allows for a two-year window, during which the two countries can either agree to renegotiate the lease for a further 20 years or end it, and this month marks the start of that period. The Tories are reportedly keen for the Americans to stay.

Labour have not stated their position, though certainly David Miliband, during his time at the Foreign Office, seems to have been very keen to make sure the evicted islanders never return, for he turned the archipelago into a huge marine conservation area, the size of France. This bans any commercial fishing, removing a key source of income for them.

The Senate Select Committee on Intelligence released a report into the CIA's interrogation practices, including at Guantanamo Bay (pictured)

Emails revealing how he forced through this controversial plan — which also very conveniently tightens security in the surrounding ocean — against the advice of senior diplomats emerged just two months ago.

It is further complicated by the Chagos Islanders themselves, still fighting gamely to return despite almost half a century in exile.

The story behind their mass expulsion — which unaccountably escaped public attention at the time — is one of the most disgraceful episodes in recent British history. The ancestors of slaves shipped from Africa to harvest the abundant coconut groves during the late 19th century, and indentured Indian servants who worked for the plantation bosses, there is no doubting their long-standing allegiance to the islands.

Yet for their own obscure reasons, the U.S. insisted that the British must forcibly remove every last one of the 2,000-plus inhabitants before delivering Diego Garcia to their hands.

The Foreign Office's latest excuse is that key documents covering the period when the rendition programme was at its height were badly damaged by water

Had the world discovered that indigenous people had been purged from their homeland to make way for a military base, there would have been an outcry.

So, ignoring the fact that they had been born and raised in long-established villages, and that many had never been off the islands, the British and Americans colluded to reclassify the Chagossians as mere ‘transient workers’ who had never really lived there at all.

Those who happened to be away in 1968, when the islands were declared ‘closed’, were never allowed back.

By 1971, amid harrowing scenes, the rest were crammed onto boats, and shipped hundreds of miles, either to Mauritius or the Seychelles. Their pet dogs were rounded up by the Americans and gassed.

Now 44, Allen Vincatassin — who was just one when he was bundled from his concrete-built home — was among many whose families were broken up by this ghastly operation. As his mother and father weren’t married and were still in their mid-teens (it was common for Diego Garcia’s people to have children very young) they were sent to separate islands where they had ties.

He went with his paternal grandparents to Mauritius, where they were abandoned, penniless, on the harbour with only the clothes on their backs. He wouldn’t see his mother again for 17 years.

Mr Vincatassin later led a long campaign for Britain to grant the right of abode to the diaspora, which he eventually won.

The island was not mentioned in the heavily redacted almost 500-page report into CIA torture released earlier this month

In 2002, the first group landed at Gatwick, and since Crawley was the nearest town, it was there — after spending several nights in the airport — that they were housed. Since then, hundreds more have arrived, bringing with them their wives and children, and their numbers have swelled to an astonishing 5,000 in Crawley alone.

A few days ago, however, KPMG (one of the world’s biggest auditing and accounting firms) published the interim findings of a feasibility study commissioned by the government to determine whether it would be viable for them to return home after all these years. The conclusion was that it would, albeit on a small scale involving just a few hundred people to start with.

Were they permitted to return to reclaim their villages — now barely visible beneath the coconut palms — Mr Vincatassin, as their elected leader, says they would gladly work for the Americans at the base, replacing the current Filipino workforce. So long, that is, as they weren’t an unwitting party to secret imprisonments and torture.

Whatever deeds were perpetrated on Diego Garcia amid the fog of war that followed 9/11, we are now assured that the only prisoners held there in recent years are fishermen who dropped their nets in the conservation area and unruly contractors working on the base.