“It is one of the most tantalising ever official accounts of an encounter with a UFO – deemed so credible it even convinced the government minister who investigated it.

Now, for the first time, the sighting of a flying saucer by an RAF fighter pilot and the subsequent high level inquiry it prompted can be revealed.

The sighting occurred in 30 July 1952, when Flight Sergeant Roland Hughes was on a training flight over West Germany in a de Havilland Vampire FB9.

As he was returning to base, he reported being intercepted by a ‘gleaming silver, metallic disc’ which flew alongside his aircraft before speeding off. The mystery object was also detected by RAF radars on the ground, which recorded it travelling at speeds far in excess of any known aircraft.

Hughes reported the sighting to his senior officers who sent him to see Duncan Sandys, the then aviation minister, to brief him personally.

Following the meeting, Sandys went on to tell senior civil servants he was convinced by the airman’s story.

The UFO sighting is not only one of the most detailed by a serving member of the armed forces but also shows how seriously such reports were taken by the authorities. British governments have historically downplayed the suggestion that such sightings have been investigated.

The existence of the sighting has emerged in papers released by the Churchill Archive, at Cambridge University. The centre contains the papers of Sir Winston Churchill, as well as Sandys, who married the former prime minister’s daughter, Diana.

In one document – written a few days after the interview with the 23-year-old Hughes – Sandys tells the government’s chief scientist, Lord Cherwell, about the meeting and states that he found the airman’s account and the supporting evidence from radar “convincing”.

The sighting came shortly after a number of similar “flying saucer” reports from US airmen and Sandys added: “I have no doubt at all that (Hughes) saw a phenomenon similar to that described by numerous observers in the United States.”

Lord Cherwell had dismissed the US sightings as “mass psychology”, but in his memo Sandys takes him to task for this attitude and makes clear his position on the existence of UFOs.

The minister, who was later promoted to Defence Secretary, went on: “Until some satisfactory scientific explanation can be provided, it would be most unwise to accept without further question the view that ‘flying saucers’ can be dismissed as ‘a mild form of hysteria’.” Sandys also wrote that there was “ample evidence of some unfamiliar and unexplained phenomenon”.

The documents are among thousands released by the archive in recent years. Their disclosures were uncovered by David Clarke, a Sheffield Hallam University academic, while he was conducting research for a new edition of a book he has written on UFO sightings for the National Archives.

By chance, shortly after his discovery, Dr Clarke was contacted by the fighter pilot’s son, who had read the earlier edition and wanted to share information about his father’s sighting.

Roland Hughes had died in 2009, aged 79, but had recounted his version of events to his son, Brian, who passed on the account to Dr Clarke, as well as his father’s log book, in which he had noted the sighting and subsequent meeting with Sandys.

The incident will now feature in the latest edition of the book, to be released in September, following the release this summer of more government UFO files from the National Archives.

In the airman’s account, relayed via his son, he was in one of four aircraft from No. 20 Squadron, of the RAF’s 2nd Tactical Air Force, returning to RAF Oldenburg, in northern West Germany, flying in formation at high altitude in clear visibility.

He reported seeing a sudden flash of “silver light” in they sky high above him which rapidly descended towards him until he could see that it was a “gleaming silver-metallic disc”.

The airman said its surface was shiny, “like tin foil”, and “without a single crease or crinkle in it”. He could see, with “astonishing clarity”, the aircraft’s “highly reflective and absolutely seamless metallic-looking surface”. He estimated its size at 100ft across – “about the wingspan of a Lancaster bomber”.

It flew alongside him for several seconds before flying off at great speed.

None of the other three pilots saw the object – it is thought because they were all executing a “banking turn” at the time and would not have been looking in the right direction – but radar on the ground had picked it up.

Six days later, Hughes – who later worked as a commercial airline pilot – was sent to RAF Fassberg, another base in northern West Germany, to give his account to senior RAF officers and Sandys himself, who was visiting. The minister’s first question to Hughes was how many beers he had had the night before.

After the sighting, Hughes – who was known as Sam, after a character created by Stanley Holloway, the actor and comedian – was nicknamed “Saucer Sam” by colleagues, who painted a cartoon of a flying saucer on his jet.

Brian Hughes, 45, a Ministry of Defence civil servant based at Bovington Camp, in Dorset, said: “We knew about the sighting in the family when we were growing up but my father didn’t talk about it a lot. We learned about it more from prompting him.

“He was very matter-of-fact about what he saw, just describing the details. He never did any research into UFO or flying saucers and didn’t have any interest in the supernatural of science fiction.

“If it was someone other than my father who had told this story, I would be sceptical. He once said to me ‘People think you’re mad if you say you’ve seen a flying saucer – I’ve only ever seen one once; I’ve never seen one since.'”

Dr Clarke, who is sceptic on UFO issues, said: “There is absolutely no doubt that something was seen by Hughes. He is not making this up. But the only honest position to take is that we don’t know what it was. But there could be some sort of scientific explanation, before you start jumping to conclusions about alien visitors.”

Further discussion of the 1952 UFO flap, Winston Churchill’s interest in ‘flying saucers’ and the debate between believers and skeptics in the British establishment can be followed in an article by Lee Spiegel published by The Huffington Post on 14 June 2012, here.