In 1950, Sir Henry Tizard, the Chief Scientific Adviser in the Ministry of Defence (MOD), became intrigued by newspaper stories about UFO sightings. Sir Henry told MOD officials that the subject shouldn’t be dismissed without first undertaking a proper scientific study. A small committee was set up at his urging. Its name: the Flying Saucer Working Party.

The committee reported in June 1951, concluding that UFO sightings could be explained as misidentifications, hoaxes or delusions. The recommendation was that no further government resources be used to investigate.

But the very next year, Royal Air Force (RAF) pilots and other military personnel witnessed UFOs during a NATO exercise. These UFOs appeared to be capable of extraordinary speeds and manoeuvres; some were tracked on military radar. By 1953, the MOD decided all UFO reports should be investigated.

Not, however, out of concern about little green men.

I worked for the MOD for 21 years. From 1991 to 1994, I was posted to a division where my duties included undertaking these investigations. It was a fascinating job, to say the least.

A UFO, it’s worth remembering, refers to any unidentified flying object – not necessarily an extraterrestrial one. While the MOD investigations were aimed at determining whether there was evidence of any threat, we were thinking more about Russians than Martians. The theory was that some sightings might involve Soviet spy planes or bombers probing our air defences to try to evaluate the effectiveness of our radar systems, aircraft and pilots. The British government’s position was virtually identical to that of the US, where UFO sightings had been investigated by the United States Air Force (USAF) since 1947, in what later became known as Project Blue Book.