The government took the threat of UFOs so seriously in the 1950s that UK intelligence chiefs met to discuss the issue, newly-released files show.
Ministers even went on to commission weekly reports on UFO sightings from a committee of intelligence experts.
The papers also include a wartime account claiming prime minister Winston Churchill ordered a UFO sighting be kept secret to prevent “mass panic”.
The files show reports of UFOs peaked in 1996 – when The X Files was popular.
The Joint Intelligence Committee is better known for providing briefings to the government on matters relating to security, defence and foreign affairs.