Floating mysteriously between the clouds, this orange-coloured disc sparked fears of extra-terrestrial activity.
The bizarre, fluorescent “doughnut” was spotted, photographed and reported to the Ministry of Defence by a retired RAF officer.
Although the UFO investigators declined to launch an inquiry – because the sighting was in Sri Lanka – they filed it away with other British “X-files.”
Details were published online yesterday in the latest batch from the files held by the National Archives in Kew, south-west London.
The unnamed ex-airman from Yorkshire saw the shape hanging in the sky near the city of Habarana, Sri Lanka, while on holiday seven years ago. After capturing it on camera, he sent it to former colleagues at RAF Fylingdales, North Yorkshire.
He wrote in his covering letter: “I noticed a partial aura in the sky, a minute or so later there was a clap of thunder.
“Then a short while later a ring like a doughnut appeared – the ring was orange in colour with a white/cream finger pushed through.
“The head of the column glowed an orange colour, behind the doughnut was a second cloud of colour, and a further ring of orange.”
He added: “The only way I can describe the sighting is that of an atomic or another type of nuclear explosion, the cloud from which did not rise in the sky, but headed from the high atmosphere down toward the earth.”
The pensioner urged his colleagues: “You must admit they are unusual.”
His letter and snaps were passed on to the X-files unit, but they wrote back saying they only had responsibility for sightings in Britain.
They told him: “Defence of Sri Lankan airspace is clearly a matter for the Sri Lankan Government and you may wish to pursue your enquiries with them.”