Expelled to make way for a US military base, John Pilger cheers the islanders fighting dirty tricks

More than 30 years ago, the British expelled the inhabitants of Diego Garcia so the US could establish a military base. Now the islanders are fighting back.

In spite of its late hour, Stealing a Nation, a documentary of mine aired on ITV on 6 October, has drawn a public reaction that suggests the invasion of Iraq has raised people's awareness as never before. Indeed, this shocking story of British government duplicity and lying, and what the Foreign Office called the "quiet disregard" of international law, allows us to understand the tragedy of Iraq.

In the late 1960s and early 1970s, Labour and Conservative governments secretly expelled the entire population of the Chagos islands, a British crown colony in the Indian Ocean, so that the main island, Diego Garcia, could be "leased" to the US for a military base. This base is now so vast that it supports 30 ships, including nuclear-armed aircraft carriers, a satellite spy station and two of the world's longest runways, from which B-52 and Stealth bombers have attacked Afghanistan and Iraq.

What happened to the Chagos islanders is a metaphor for the behaviour of "our" governments beyond the protective screen erected by much of western journalism and scholarship. Nearly 2,000 people trace their families back to ancestors who first lived on the islands in the 18th century; they came originally from Africa and India and developed a unique Creole civilisation with thriving villages, a school, a hospital, a railway, docks, a copra plantation.

In 1964, a joint Anglo-American team surveyed the islands for a base that would be the Pentagon's "platform" in the Indian Ocean. Foreign Office cables emphasised the need for secrecy, worrying about the "damaging publicity" should the plan become public. Documents found recently show that, at a meeting between Foreign Secretary Michael Stewart and Secretary of State Dean Rusk in 1966, a conspiracy was approved by the two governments whereby the deportation of the islanders would be concealed both from parliament and the US Congress. No payment was recorded for the "lease" of the islands; instead, the Royal Navy was given a $14m discount on an American Polaris nuclear missile.

At first, the islanders were tricked into leaving and prevented from returning. By 1973, those who remained were herded on to ships, with the women and children below deck with a cargo of birdshit. They were dumped in the slums of Mauritius, more than 1,000 miles away, where poverty, suicide and drugs have blighted them. Lisette Talate, now in her sixties, told me: "I lost two children, who died of sadness. Doctors cannot treat sadness."

The conspiracy revolved on the lie that the islanders were merely transient workers from Mauritius and the Seychelles and therefore could be "returned". This was the equivalent of "returning" the majority of Australians, whose forebears had arrived in the same year, 1770, as the first islanders settled in the Chagos. The evidence has long been available at the Public Record Office. To my knowledge, no journalists and only one academic, the historian Mark Curtis, bothered to look for them. Moreover, the documents displayed in Stealing a Nation are merely the top of a pile. Here is a selection:

A 1965 Foreign Office memorandum describes how Washington made expulsion of the entire population "virtually a condition of the agreement when we negotiated it". Another says that as the British government is open to "charges of dishonesty" it is vital to "cook the books". As for the islanders, wrote one official, "these people have little aptitude for anything other than growing coconuts". They are, wrote Sir Bruce Greatbatch, later governor of the Seychelles and responsible for depopulating the islands, "unsophisticated . . . untrainable". In other words, expendable.

From 1965, British embassies around the world were instructed to avoid all reference to "permanent inhabitants" in the Chagos. The islanders, wrote one official, were to be "converted" to a "floating population" who would vanish under a policy of "quiet disregard". In 1968, Foreign Secretary Stewart wrote that "by any stretch of the English language, there was an indigenous population, and the Foreign Office knew it". Yet, on 21 April 1969, in a secret minute to Harold Wilson, Stewart proposed that the government lie to the United Nations "by present[ing] any move as a change of employment for contract workers . . . rather than as a population resettlement". Five days later, Wilson gave his approval, which was copied to senior members of the cabinet.

A Foreign Office memo recommended: "Should a member [of the House of Commons] ask about what should happen to these contract labourers in the event of a base being set up on the island, we hope that this can be brushed aside as a hypothetical question."

In 2000, following an epic struggle from the depths of their dislocation and poverty, the "unsophisticated" islanders won a landmark victory in the High Court, which ruled their expulsion illegal. The Blair government has since prevented them from going home with a filibuster of nonsense about the islands "sinking" - perhaps under the weight of the thousands of American servicemen and their bars, barbecues and bombers in an environment that the US navy describes as "outstanding".

According to the Washington Post, there is a Guantanamo Bay-type "facility" on Diego Garcia. The Blair government has denied this. The author of the Post investigation said: "What we have from our sources is that some al-Qaeda suspects are indeed being held and questioned at Diego Garcia. The British government could go some way to clearing this up by permitting an unrestricted visit." Along with the population, human rights groups and journalists are banned from the island.

On 10 June last, election day for local authorities and the European Parliament, a politician called Bill Rammell, now a junior Foreign Office minister, slipped a written statement in to the Commons announcing that the Queen had approved an "order in council" banning the Chagos islanders from ever going home. This was the same archaic royal prerogative, or decree, used to deport them more than 30 years ago. In August, Rammell told me that "the British taxpayer" cannot possibly find the few million pounds that would fund the return of the islanders. Instead, the British taxpayer pays for a lavish British diplomatic presence in Mauritius, just a few streets away from the slums of the Chagos islanders. I asked him if he felt any shame for the actions of his government. No, he replied, unsurprisingly.

On 7 October, however, the High Court agreed to a judicial review of Rammell's royal decree; the Foreign Office will need to pull out new tricks to win this one. The islanders and their London lawyer, Richard Gifford, say that, if necessary, they are heading for the European Court of Human Rights. All decent people should support them.

When the islanders came to Britain for the last High Court case, the defence kitty could afford only pretty basic accommodation; some are women in their seventies. If you would like to help, you can give to the Ilois (islanders) Support Trust (www.iloistrust.org). The bank account is National Westminster no 90213319; sort code 60-30-06. Those who missed Stealing a Nation can order a videotape by writing to: Video Library, ITV1, Gas Street, Birmingham B1 2JT

John Pilger, renowned investigative journalist and documentary film-maker, is one of only two to have twice won British journalism's top award; his documentaries have won academy awards in both the UK and the US. In a New Statesman survey of the 50 heroes of our time, Pilger came fourth behind Aung San Suu Kyi and Nelson Mandela. "John Pilger," wrote Harold Pinter, "unearths, with steely attention facts, the filthy truth. I salute him."