A new book has revealed how Britain's most successful UFO hoax sparked a nationwide panic in 1967, and duped even the highest echelons of Whitehall.
Files released by the National Archives this week revealed the aliens landed on the green of a golf course near Bromley, in South-east London, some fields scattered across southern England and a hill in Somerset.
It was a small armada of six flying saucers that arrived on September 4, 1967, and the crafts were made of shiny plastic pods that looked like gigantic fried eggs.
The hoax caused panic among intelligence agents, senior police officers and top-flight mandarins. And it put Britain on alert for a full-scale interstellar invasion.
"It was the most effective and elaborate flying saucer hoax ever perpetrated in the world. And the hoaxers did it all for 30 pounds," the Daily Mail quoted the book's author John Keeling as saying.
The hoax exposed the fact that at the height of the Cold War, the British authorities had no idea how to respond neither to an alien invasion nor to an attack by a human foe using unconventional weapons.
There were 360 British "sightings" that year of 1967, nearly one a day, and the media were taking the subject of extraterrestrials seriously.
It was the perfect time for a handful of clever, mischievous trainee engineers from the MoD's Royal Aircraft Establishment at Farnborough in Hampshire to perpetrate one of the most audacious pranks in student history.
The ringleaders were Christopher Southall and Roger Palmer, both aged just 21, and the prank had been conceived to raise money for charity as part of the college's Rag Week.
But the team had a second, darker motive. They wanted to see how the authorities would react if there was an alien invasion, and to find out just how prepared Britain was.
The Farnborough Rag committee agreed to the plan in January 1967. But it would not be until September that the invasion would be launched.
The students constructed six oval flattened objects, 54in long, 30in wide and 20in deep, moulded from fibreglass and laced with artist's graphite to give them an otherworldly sheen.
They decided that they would have to have something "alien" inside them before they were sealed up. So they concocted disgusting jelly-like goo made from bread dough boiled at a high temperature.
It looked like mashed human brain and stank to high heaven. Anyone who tried to break open one of the UFOs was going to be in for a nasty - albeit harmless - surprise.
Also inside each saucer, which weighed about a hundred and just about fitted in the back of a car, was placed a small electronic loudspeaker, programmed to emit an unearthly wailing noise if the UFO was disturbed.
Once all the crafts were found, the MoD took over, but the first thoughts in Whitehall were not, in fact, of aliens, but of Soviet weaponry.
Britain's top intelligence officers and policemen were mobilised and decided to keep the saucers secret, but news had already broken.
In the end, the hoaxers' cover was blown, not by a top detective or MI5, but by a newspaper reporter who knew that the Farnborough students had form.
Towards the end of that extraordinary day, the hoaxers held a press conference, at which they admitted their guilt.
"We believe that flying saucers could land one day, so we landed our own to give the authorities some practice," they stated.
The police and government bodies looked ridiculous. They were furious and there were threats of prosecution.
As a result of all the publicity, the students raised about 2,000 pounds for charity, and they received offers from all over the world for the surviving saucers.
