Haut came to the town of Roswell (population 50,000) with the Army Air Force during the Second World War. The town’s slow pace and traditional sense of community had suited him so well he had stayed there for the next 60 years, working first as an insurance agent and later running an art gallery and frame shop in the centre of town. In many ways, with his local committee memberships, his successful business ventures and his string of civic awards, Haut was Mr Small Town America – Richie Cunningham’s dad made good in the dusty New Mexico sun. Pallbearers at the funeral included even Bill B Owen, the town mayor.

But this seeming normality belied an eventful past. For Haut came to Roswell with the 509th Bomb Group, the elite US bombing crew who dropped the atom bombs at Hiroshima and Nagasaki; Haut himself was a bombardier, participating in 20 bombing raids over Japan and entrusted with dropping the measuring instruments during Operation Crossroads, the nuclear tests at Bikini Atoll in the summer of 1946.

More intriguingly, Haut was public information officer at Roswell Army Airforce base who, apparently on the go-ahead of his commanding officer, in 1947 issued local media with the famous press release reporting the recovery of a crashed flying saucer on a ranch 75 miles outside of town – the story was broadcast by local radio stations, went out on the wire and was picked up by just about every evening newspaper west of Chicago. “RAAF Captures Flying Saucer On Ranch” declared the front page of the Roswell Daily Record.

Exactly what happened next has been debated endlessly. Certainly, somebody somewhere hit the panic button. The next day, Associated Press would report over the wire that the army and navy had begun “a concerted campaign to stop the rumours” and, within hours, the original press release had been rescinded, replaced with talk of a crashed weather balloon. In Fort Worth, Jesse Marcel, the Roswell base intelligence officer, was paraded in front of press cameras, presenting as recovered wreckage pieces of all-too-obvious weather balloon. The brief summary in the base’s record for July 1947 is a study in blandness. “The Office of Public Information was quite busy during the month answering inquiries on the ‘flying disk’,” it noted. “The object turned out to be a weather balloon.”

Case closed, in other words. And while in Roswell itself old timers occasionally referred to the incident in conversation, elsewhere it was forgotten – until that is, the Seventies, when nuclear physicist turned UFO researcher Stanton Friedman stumbled on the case.

“I was at a TV station in Baton Rouge, Lousiana, in 1978,” he says. “I was waiting to be interviewed but the reporter was nowhere to be found. While the station manager is being apologetic and giving me coffee, out of the blue he says, you know, the guy you gotta talk to is Jesse Marcel.”

Friedman phoned Marcel from a payphone in Baton Rouge airport the next day – and was amazed by what he heard. From this point on, the researcher began to wonder if the sleepy ex-air force town might just be Space Port One. “Basically, it was one of the most important events in man’s history, the recovery of a crashed flying saucer, including the recovery of alien bodies,” he says.

“Well, naturally they covered it up. I mean, this was 1947. The Second World War finished only two years earlier, the world was in chaos – Europe didn’t have enough food, shelter or clothing. You can hardly tell the world ‘there are these alien spacecraft penetrating our airspace and we can’t do a darned thing about it’. And you have to consider, this is New Mexico – where the Manhattan Project took place, home of the White Sands missile range. Secrecy was a way of life down there.”

In the late Seventies and early Eighties, Friedman and his colleagues tracked down 90 people with a connection to events, including pillar of the community and unrepentant believer Walter G Haut. Sceptics have pointed out the post-war years were excitable times – radar was a new invention and UFOs were a vogue topic in those first years of Cold War paranoia. The crash at Roswell in particular was reported amid an atmosphere of mounting excitement nationwide.

The term ‘flying saucer’ had been coined only three weeks before, after a pilot named Kenneth Arnold reported an encounter with “a chain of nine peculiar aircraft (appearing) to be completely round” over Washington State. It is no exaggeration to say saucer-mania was gripping the nation – and, indeed, a Gallup poll of the next year would find that while half of Americans had heard of the Marshall Plan, America’s flagship programme to rebuild post-war Europe, a full 90% understood the term ‘flying saucer’.

Ufologists, of course, have their own explanation for these many sightings, but where everyone agrees is that Roswell was the scene of a determined government cover-up. Local rumour talked of mysterious phone calls to journalists, of the rancher who originally found the site being held incommunicado for seven days, even the harassment of a team of archaeologists thought to be digging near the supposed site. Ongoing local resentment continued into the Nineties, finally coming to the attention of Steven Schiff, US congressman for New Mexico.

Determined to discover what really happened, Schiff went to the investigative arm of Congress, the General Accounting Office, asking them to investigate the case using all available records. Faced with possible embarrassment – or exposure? – the US Air Force set up an investigation of its own, to be conducted by Colonel Richard L Weaver. With access to classified files, Weaver’s report revealed that, yes, there had been a crash and cover up – though not of a UFO. The rancher had indeed found a balloon, Weaver asserted; but attached to it had been classified electronic equipment designed to record airborne radiation. It was part of a top-secret operation – Project Mogul – the goal of which was to detect nuclear testing in the Soviet Union.

Stan Friedman thinks he just smells a whole new rat. “The Mogul balloon explanation doesn’t work for several reasons,” he argues. “They keep saying the wreckage was found on June 14. But these would be neoprene balloons, not the polyethylene ones you see on TV today; they would have disintegrated in the air by July 8. At the same time, Weaver says Mogul was high security – yet several other of the launches were just allowed to die in the desert, without chase teams.”

He also argues Weaver’s use of evidence was selective, to say the least – all of which is grist to the mill for conspiracy theorists and believers worldwide. It’s hard to know exactly what to believe, but what no one can deny is that modern interest in the historical event has transformed the economy of downtown Roswell. “Before the world became interested in the Roswell incident, the town had a very limited tourist base,” says Julie Shuster, director of the International UFO Museum and Research Centre. “Now we average between 150,000 and 170,000 visitors a year.”

Twenty thousand of these visitors come over a single weekend in early July to attend the annual UFO festival, a packed assortment of lively debates, concerts (country music features prominently) and, as centrepiece, a colourful night parade of UFO-themed floats, complete with spotter planes criss-crossing overhead hoping for a glimpse of the most eagerly anticipated visitors of all.

“The tourist interest has brought in spin-off businesses to Main Street – T-shirt shops and so on,” says Shuster. “And, you know, Roswell’s kind of in the middle of nowhere; the nearest major community is 200 miles away. So, at the very least, everyone who comes here is going to need to buy gas and Coke.” According to local figures, the museum and festival combined are worth more than $60 million a year – and where only 15 years ago the town’s Main Street area experienced vacancy rates of 60-70%, four out of five shops are now occupied.

Interested locals are keen to stress the sober research function which underlies the rubber-suited fun of the summer festival and are particularly sensitive to accusations of what we might call Nessie-fication – the notion the locals dreamed the whole thing up in the local bar, all in the name of tourist dollars.

Whatever you make of the residents’ own claims, there is no denying Roswell has attracted more than its fair share of opportunists and chancers over the years. Best known is London-born film-producer Ray Santilli – a colourful character whose story forms the subject of forthcoming British film, Alien Autopsy, starring Ant and Dec. With a script written by William Davies (credits include Shameless), Alien Autopsy is a comedy based on Santilli’s exploits in the mid-Nineties, when he grabbed the attention of the world’s media by claiming to possess Roswell Incident-era video footage which showed government scientists conducting an autopsy on a captured alien life form.

Santilli, who is played by Dec in the film, claimed to have acquired the footage from the original military cameraman in Cleveland, Ohio, in 1994. At the time, the Londoner’s core business was repackaging cut-price archive footage of famous performers for the mass-market and he had originally contacted the cameraman hoping to buy unseen footage of Elvis. Apparently the elderly cameraman came up with a far more intriguing proposition. He claimed at his Florida home to possess a copy of the autopsy footage, left in his hands after a bureaucratic blunder – and he was willing to sell it for $30,000.

Money wasted? Not for a minute. Santilli proceeded to sell the footage to media outlets around the world, allegedly netting $200,000 from his sale to the Fox network alone. For their money, the TV stations received 15 minutes of grainy footage. Two doctors in protective suits are shown gingerly inspecting and then opening up a single alien corpse, removing a succession of indistinct internal organs. The alien has an oversized head, six fingers and suitably beady eyes. At one point, the camera glimpses a shadowy figure who may or may not have been President Truman.

Unsurprisingly, the Santilli footage immediately caused a stir among Roswell researchers. Popular theories already considered the recovery of alien bodies at the Roswell site – an undertaker in town claimed to remember receiving a request from the air force base for child-sized coffins and researchers tracked down the Mexican driver who claimed to have ferried the then Governor of New Mexico to and from the base in 1947. Apparently, Senator Montoya emerged from one such visit mumbling about “two little men”, so shaken that the driver had to take him home and feed him a bottle of Jim Beam.

But as the months went by, the initial excitement of the UFO community gave way to disappointment. Ultimately, Santilli was unable to come good on his promise to have Kodak independently verify the age of the film and, while medical experts questioned technical aspects of the autopsy, special-effects engineers lined up to second guess how the film might have been made.

Stan Friedman’s doubts stem from his own experience working under top-secret conditions as a nuclear physicist. “The notion that a cameraman would be able to keep a copy, or portions of the original footage, seems totally absurd. You don’t get to keep copies! The fear of death is put into you about keeping classified documents. They could charge you with treason!” he says.

All of which has led to very mixed feelings about Ray Santilli. At the time, many were convinced of Santilli’s good faith, even when faced with evidence to the contrary. While directing a documentary about Roswell for Channel 4’s Secret History season, filmmaker Tim Shawcross accompanied Santilli to the US. “He comes across as one of the most plausible people I have ever met,” Shawcross wrote of Santilli at the time. “When he felt I was becoming increasingly sceptical about the entire nature of the ‘alien’ footage, he expressed hurt and dismay that I should not believe him and seemed genuinely taken aback.”

When the story broke, Stan Friedman invited himself over to London to visit Santilli on his own turf. “I knocked on the door of his office; there’s not even a name plate on the door of the company. Then he hustles me off to a coffee shop down the street,” Friedman recalls. “It turned out just about everything Ray told me in that first conversation wasn’t true.”

Most troubling to researchers like Friedman was the pattern of escalating lies – the almost desperate rearrangement of facts to cling on to credibility. “Whenever I pointed out something which challenged what he called the facts, he’d change his story,” says Friedman. The lowest point came live on French TV. Under increasing pressure to release the name of the cameraman, Santilli had hinted at one Jack Barnett, a former Fox Movietone cameraman. With cameras rolling, TF1 host Jacques Pradel confronted Santilli with evidence that Barnett had never been associated with the military. In fact, Barnett had died in 1967 – and Santilli’s position was slipping away. In 1998, Fox revisited their expensively acquired Alien Autopsy footage but this time in a show counting down the greatest hoaxes of all time.

Alien Autopsy, the movie, offers a whole new realignment of facts – all framed by vague claims the plot is based on real events. While, according to the Internet Movie Database, Santilli produced his first documentary, The Life of Bruce Lee, in 1993, the on-screen ‘Ray Santilli’ has morphed into a cheeky-chappy market vendor, flogging home-made pirated videos for a living. Again, he buys the footage in Cleveland and, again, it is the genuine article. Now, however, the footage is destroyed in transit to the UK, forcing Santilli and friends to hastily shoot a fake autopsy of their own to avoid the wrath of the sinister drug baron they brought in as investor. Credit for the hoax, then – but still maintaining there was once a genuine tape.

Probably it shouldn’t be taken too seriously. Nevertheless, you have to admire Santilli’s chutzpah – after all, the movie’s not just about him, his name also turns up as executive producer. “Ray may be devious – but he’s sharp!” Stan Friedman says with a laugh. “What can I say? I used to live in California.”

And as Roswell prepares for a whole new wave of British interest, riding on the backs of Ant and Dec, Friedman acknowledges the debt which the town and the field of Roswell studies owes to the original Santilli media event. “On one level, the original Santilli footage functioned as a sort of blot-out for the noisy negativists – it let people suggest the whole thing was phoney baloney,” he says. “But it’s certainly been positive in the way it has stimulated interest in Roswell in the media and beyond.”

Alien Autopsy is released on April 7