What was that strange crimson object seen in the night sky near Old Deer Road in Peterhead in January 1982? What became of the spherical object, described as "very bright with a long tail" reported by the Kirkwall coastguard on January 25, 1985?

The truth about what's out there and what the British Government really knows about Unidentified Flying Objects is revealed in the real-life version of the X Files released to the public today.

The first collection of Ministry of Defence files detailing sightings of strange objects in the sky have been released after a Freedom of Information campaign by UFO researchers.

Over the next four years, more than 150 files will be thrown open making the UFO files the largest collection of papers under 30 years old ever released by the Ministry of Defence.

To the disappointment of conspiracy theorists the files seem to conclude that the military know nothing more than the rest of us about alien visits but, when pressed, came down on the side of the sceptics.

The MoD has been collecting information on UFOs since the early 1950s but other than establishing whether the phenomenon reported to them constituted a threat to national security, the military took little interest in stories of bright lights, saucer-shaped aircraft, and little green men.

The mixture of documents, reports and files released to the National Records Office run in chronological order covering the 1970s and 1980s and detail what members of the public have seen.

Whether you believe in aliens or not, the sample of the 11,000 or so reports received makes for intriguing and sometimes amusing reading.

While many sightings were made by ordinary members of the public those filed by pilots and military personnel attracted most interest from the MoD and were sometimes further investigated for corroboration by radar data.

The UFO reported by the coastguard in Kirkwall, for example, was confirmed by the coastguard in Aberdeen who saw the object split in two.

A sighting by an airline pilot of an object passing 1.5 miles from the port side of the aircraft moved him to write to the MoD asking whether it could be ascertained as space debris, a comet or a missile. "If it is a missile, myself and my crew are not impressed," wrote the pilot.

On Christmas Day, 1985, a group of policemen led by an inspector reluctantly reported seeing "a bright light like a meteorite" falling on Horsell Common in Woking which, they were only too well aware, was the setting for a Martian invasion in H G Wells's The War of the Worlds. The policemen scribbled in the margin of their report: "This is a genuine report - two competent police officers, slightly embarrassed."

The House of Lords held a whole-day debate on the subject of UFOs in 1978

The vast majority of reports are from ordinary people who contacted the MoD because they simply saw something in the night sky.

But some claim to have been abducted by aliens. Scotland's most infamous abduction case was the sighting by Bob Taylor on November 9, 1979, in Dechmont Law, near Livingston, which has gone down in history as one of the world's most remarkable encounters.

Mr Taylor, a 61-year-old forestry worker, was doing his rounds of the woods overlooking the town when he came upon a clearing.

There, apparently, a few feet above the ground, hovered a disc-shaped spaceship.

As Mr Taylor stared in amazement, two spiky balls dropped from the UFO and moved towards him making a plopping sound as they went. The objects grabbed his trousers.

He fell to the ground. When he came to 20 minutes later the UFO had gone.

Many people claim to have been involved in the classic alien abduction phenomenon but one file released shows how this went awry for an elderly fisherman in Aldershot.

The man, in his 80s at the time, saw a spaceship land by the side of the Aldershot canal. He was invited aboard by creatures in green overalls to inspect their ship only to be told that he was too old and infirm to be taken for a spin.

A Cheshire man wrote to the MoD claiming that he had physical and psychic contacts with an alien, Olgar by name, for most of his life. Unfortunately, Olgar was killed in a battle with other alien beings in 1981 so could not corroborate the story.

The hapless MoD official who dealt with the correspondence stamped it "no reply". In fact there is no evidence that any of these contact reports with aliens were followed up by the Ministry of Defence.

If you think Cheshire man's file is odd, some fairly bizarre stuff was going on at parliamentary level, too. One document relates how the House of Lords held a whole-day debate on the subject of UFOs in 1978.

At the time the country was going through the Winter of Discontent, bodies were not being buried and rubbish was piling up on the streets. But the Lords pressed on with a debate aimed at persuading the MoD into opening a public inquiry into the UFO mystery. This was, remember, shortly after Steven Spielberg released his alien movie Close Encounters of the Third Kind which led to a doubling of UFO sightings.

The background notes prepared for the government ministers show that the MoD had decided to take the subject seriously. The government policy on UFOs, emphasised again and again, is that it is not interested in the scientific basis of the phenomenon.

The basic policy was to determine whether anything reported could be an enemy aircraft. If it wasn't Russian then the MoD didn't seem to care if flashing lights in the sky were Martian or Venusian.

The US military also took UFO sightings very seriously, setting up Project Blue Book to collect several thousand UFO reports in the 1950s. This material was subject to a University of Colorado study which concluded that 90% of sightings could be explained by man-made and natural phenomena and Project Blue book was closed in 1969.

The MoD, however, continues to receive and investigate sightings across the UK up to the present day and occasionally looks into them in a little more detail.

The batch of MoD files released today also contain further details of the Rendelsham Forest incident, referred to as Britain's Roswell, which took place in December 1980 outside RAF Woodbridge, a US Air Force base in Suffolk. The incident involved the base deputy commander, Colonel Charles Holt, and guards reporting a strange glowing object in the perimeter of the base hovering on three legs. It vanished and was seen again at another gate. The next day three depressions were found in the ground.

The radar traces showed nothing unusual on the night and the MoD was dismissive of the incident. "I think you will agree that it is highly unlikely that any violation of UK airspace would be heralded by such a display of lights," noted one official caustically.

So much for a cover-up then? "The very fact that these documents have been released show that there has been no cover-up by the MoD," said Dr David Clarke, journalism lecturer at Sheffield Hallam University, who has been campaigning for the file's release. "It's a good move by the MoD to actually put this material into the public domain and demonstrate what they know - which doesn't amount to much."

So is the truth out there? The closing remarks in the MoD briefing for the House of Lords debate on the subject sum up the official attitude quite neatly: "As for telling the public the truth about UFOs, the truth is simple. There really are many strange phenomena in the sky and these are invariably reported by rational people. There is a wide range of natural explanations for these phenomena. There is nothing to suggest to Her Majesty's Government that such phenomena are alien spacecraft."