(Above) A Toblerone-shaped UFO. © The National Archives
The National Archives has released the fifth and largest instalment of confidential UFO files to date, comprising 24 Ministry of Defence papers in 6,000 pages of material from 1994 to 2000.
Incidents covered include Toblerone-shaped UFOs, unidentified white substances and mysterious diseases reported from sites around the UK.
In 1997, a Birmingham man arrived home at 4am to be confronted by a large blue illuminated blue triangle hovering above his garden.
When it shot off, leaving a silky white substance on the treetops, the man stored a sample of the material in a jam jar, but the report does not say what happened to the mysterious sample.
In the same year, a luckless Welsh motorist was driving home late at night when his car was suddenly enveloped in a mysterious tube of light, showering the car in dust and dirt.
The man returned home, where he was physically sick, and later developed a mysterious skin condition which required medical treatment.
The interior of a possible UFO with three aliens at the controls, seen from aircraft over India. © The National Archives
Dr David Clarke, author of The UFO files and Senior Lecturer in Journalism at Sheffield Hallam University, has written an introduction to the files. He said many of the sightings may have been influenced by what people had read and watched.
"In the 1950s the next big leap in technology was thought to be a round craft that took off vertically, and it's intriguing to note that this is the same period when people began to report seeing 'flying saucers' in the sky,'" he suggested.
"In the period the latest file release covers (1994-2000), triangular-shaped US stealth bombers and Aurora spy planes featured heavily on TV (The X Files 1993-2002) and films (Independence Day, 1996) and the shape of reported UFOs corresponds.
"It's impossible to prove a direct link between what people are reading and watching and what they report as UFOs, but one interpretation could be that the latest advances in technology may be influencing what people see in the sky."
The files are available to download for free for a month from the National Archives website. The site also hosts a videocast dramatising highlights from the files alongside a detailed guide to researching the files by Dr Clarke.