The United Kingdom's National Archives has unveiled a new slew of UFO-related documents, including papers describing Winston Churchill's cover-up of a UFO sighting during World War II. The Prime Minister massively soft-pedaled the encounter to avoid public hysteria.

Among the declassified documents is a letter from 1999 in which the grandson of one of Churchill's bodyguards claims that the Prime Minister withheld reports of an RAF aircraft's run-in with a UFO:

The National Archives also has a PDF document that notes the juiciest tidbits, and here are some other highlights from the BBC:

* [A] near-miss with an "unidentified object" reported by the captain and first officer of a 737 plane approaching Manchester Airport in 1995.

* A mountain rescue team called to investigate a "crashed UFO" in the Berwyn Mountains in Wales in 1974.

* Attempted break-ins at RAF Rudloe Manor in Wiltshire - sometimes referred to as Britain's "Area 51" - the US's secretive desert military base.

* The Western Isles incident, when a loud explosion was reported in the sky over the Atlantic in the Outer Hebrides.

* The 14-minutes of "missing" film relating to the Blue Streak missile test launch in 1964, believed by some to show a "spaceman".

* A gambler from Leeds who held a 100-1 bet on alien life being discovered before the end of the 20th Century, and who approached the government for evidence to support his claim after the bookmakers refused to pay out. The MoD said it was open-minded about extra-terrestrial life but had no evidence of its existence.

[National Archives via Foreign Policy. Top photo from the Doctor Who episode "Victory of the Daleks."]