Is there anybody out there? The Ministry of Defence, it seems, is taking no chances. Files containing hundreds of previously classified reports are being released today in the hope of persuading ufologists that there has been no cover-up regarding the existence of visitors from outer space.

Yet the files do show that the MoD conducted a rigorous investigation of every alleged sighting of a UFO until well into the 1980s. In a briefing note in 1979 the MoD wrote: “Her Majesty’s Government has never been approached by people from outer space.” But the Defence Intelligence Staff was given the task of following up sightings, interviewing witnesses, collating information and filing reports.

Unlike the United States, which decided in 1969 that UFOs did not present a threat, and that 90 per cent of sightings could be explained as natural phenomena, Britain kept the files open, and the hundreds of cases reported each year were examined by police and then passed to the MoD.

Publication of the files reveals that thousands of members of the public have had X-Files moments. Some sightings were given short shrift, such as that of the elderly gentleman fishing near Aldershot who informed the authorities that a spacecraft had landed close by, and that little men in green overalls had approached him and invited him on a tour of their ship.

A woman from Sanderstead in Surrey, peeping out from her bedroom window at 3am, in June 1983, saw a large rectangular-shaped object passing slowly. “There seemed to be no means of propulsion. The object was not being pushed, pulled, lifted or carried — its movement was silent,” she reported. She drew a picture of what she had seen and it appears in one of the eight files of reports released yesterday by the National Archives in Kew. Another 150 files are to be released in the next three years.

Many policemen were witnesses of the UFO sightings. In one case in April 1984, the police at Edgware, North London, were summoned to investigate a bright light in the sky that was flashing “blue, white, green and pink”. There then appeared a “blinding white ball with a tail” which sent women screaming into their homes.

The file, written up by a police officer, recorded: “A pair of binoculars was obtained and I studied the object through them. I saw that the object was circular in the middle with a dome on top and underneath. The middle section of the object had bright blue lights around it with a red or pink light on the extreme right. The dome on the top had blue and white flashing . . . We observed the object for one hour.”

Preparing a draft speech for a minister who had to give the Government’s response to a debate on UFOs in the House of Lords in 1979, the MoD wrote: “There is nothing to indicate that ufology is anything but claptrap [but ]the subject will not go away.”

Lord Clancarty, who had asked for the debate, believed that a famous Norfolk regiment had disappeared into a cloud in the Gallipoli campaign in the First World War and put it down to UFO activity. The MoD briefing note had in brackets, “checking with Army Historical Branch”.

The MoD draft went on: “Not a single artefact has been produced, not a single extraterrestrial chap has dropped an extraterrestrial spanner . . . [but] Lord Clancarty has the answer — the CIA has hidden them all.”

However, the MoD acknowledged: “Intelligent life could exist elsewhere in the universe. With 100,000 million stars in our own galaxy alone, it’s probable that there are many planets capable of supporting life. \ the technical difficulties in inter-stellar travel are stunning. Even at the speed of light it would take four years to reach the nearest star and 100,000 years to cross our galaxy.”

Reported sightings

— December 1981, Colwyn Bay, North Wales A blob, bright, no sound, is seen

— November 1981, near Burford, Oxfordshire A stream of seven to eight lights, white, red and blue, looked “extraordinarily big”

— September 1984 on the A839 to Lairg in the Highlands A bright star-shaped object 6ft above the ground and 4ft from a car on the driver's side, travelling at 30mph

— May 1984, at Benhar, Lanarkshire A star-shaped object flashing orange, white and green is seen by a reporter

— December 1983, at Peacehaven, East Sussex A 50p-shaped object with lights and windows is seen heading for the sea

Times Recommends

• Alex Rider exclusive: Incident in Nice
• Green & confused: do energy-saving bulbs work?
• Let’s skip lunch, say the hungry generation