A former head of the Armed Forces wrote to the defence secretary urging him to “demonstrate a more serious concern” over a now famous UFO sighting, files released by the Ministry of Defence disclose.

The incident is just one among the hundreds of reports of UFO close encounters, from aliens with lemon-shaped heads to laser beams being shot to earth, contained in the files.

Other episodes include when two “sober” Glastonbury festival goers saw a flying saucer hover overhead and dozens of sightings which turned out to be a Virgin Airship and two boys who claimed an alien told them: "We want you, come with us".