Okay, so I changed my mind…
In 1947, three UFOs crashed in Roswell, New Mexico. The Military recovered… erm.. one saucer-shaped craft and the bodies of three dead alien life forms and took them… somewhere or other and performed top top secret autopsies on them. The military used Russian Civilian Gasmasks which were not available til the ’70s, and tools widely available in B and Q to perform these autopsies, which took place in a tent, lab and I’m pretty certain a train carriage too (cos the X Files is actually a hard-hitting reality TV series.) This whole operation was secretly filmed, using processes only available from the ’80s onwards, and then leaked to coincide with the release of several popular UFO related films.