Yet the weird wreckage found on a remote hillside in Scotland has been revealed as a top secret CIA spy balloon destined for Russia.

It was found in 1962 by shepherd Donald McKenzie. Three months went by before the RAF reluctantly dispatched a mountain rescue team to check it out.

What they found has gone down in UFO history as Britain’s Roswell – a reference to a flying saucer flap caused by a balloon in New Mexico in 1947.

The four-man RAF team found a strange box-like object lying in the heather at Ardgay, in the Highlands.

It had a camera port but the camera had been removed. The team spotted other signs someone else had beaten them to the crash site.

When Squadron Leader John Sims called the Air Ministry he was told by London he had “no need to know" what had happened. The mystery deepened when the team was ordered to alter their records to delete all reference to the incident.

Now Britain’s X files expert Dr David Clarke claims to have solved the mystery in his book, How UFOs Conquered The World, out on May 14. During a trawl of Air Ministry documents in Kew’s public records office, he came across a file marked Top secret – USAF meteorological experiments. 

It revealed details of a spy programme codenamed Moby Dick bankrolled by the CIA from 1955-56. It involved a Scots-based US weather team using balloons to lift fibreglass gondolas into the stratosphere to be carried by the jet stream across Russia.

Soviet MIG fighters found it hard to intercept the balloons but the Scottish weather did the job for them. This one had blown off course after its launch six years earlier.

Dr Clarke said: “The Pentagon had spent $68million on this and was determined to keep it a secret.”