The order came straight out of the Cold War manual: "Arm all weapons and fire on sight." For Lieutenant Milton Torres, an American jet fighter pilot based in Britain, it was the first and last time that he had received such a chilling instruction. As soon as he scrambled his Sabre jet from RAF Manston in Kent and headed eastwards, he saw the blip on his radar, indicating the presence of an aircraft the size of a B52 about 15 miles away, and he prepared to close in for the kill with a salvo of rockets. But the "aircraft", judged to be hostile and probably Russian, simply vanished. The blip on the radar disappeared. The 24-year-old American pilot's extraordinary experience on the night of May 20, 1957, which he was officially ordered never to reveal to anyone, has come to light after the declassification of another batch of Ministry of Defence files relating to reported incidents of unidentified flying objects appearing in British airspace in this case the only known example of a jet fighter pilot being ordered to shoot down a UFO. Mr Torres, now 77 and a retired professor of civil engineering living in Miami, told The Times that the day after he was scrambled from RAF Manston he received a visit from an American in a trenchcoat who waved a National Security Agency identity card at him and warned him that, if he ever revealed what had happened, he would never fly again. He took the warning to heart and said nothing until 1988 when, through a solicitor with an interest in ufology, he sent the Ministry of Defence a report giving a full account of the incident. Today his narrative is released by the National Archives.