A US Air Force fighter pilot claims he was ordered to fire all of his 24 rockets at a UFO spotted flying over East Anglia - and then warned never to speak about the incident - the MoD records reveal.

Milton Torres, then aged 25, was on standby at RAF Manston in Kent on May 20 1957 when he received an urgent order to scramble and intercept an unknown craft with "very unusual flight patterns".

He managed to get a radar "lock-on" the target, which he could not see because of thick cloud but which his instruments indicated was the size of a B-52 bomber.

The order then came through to fire his jet's entire arsenal at the UFO, but it darted off his radar before he could act.

Dr Torres, now 77 and still convinced it was an alien craft, says he was visited the next day by a man claiming to be from the US National Security Agency, who threatened him with losing his flying status if he told anyone what happened.

The former pilot's story entered the MoD's archives after he repeated his claims at a veterans reunion in 1988.

"There are people who are still alive on Earth who know about this," he said.