When forestry worker Robert Taylor reported seeing an alien spaceship in woods near Livingston 40 years ago it made headlines around the world.
The Dechmont Woods incident is unusual among reported UFO sightings in that it was investigated by the police.
They treated the rips to Mr Taylor's trousers as evidence of an assault but could never quite work out what had happened to him.
In his testimony to the police, the 61-year-old described how he saw a 30ft-high "dome-shaped" object in a clearing in the forest near the West Lothian new town on 9 November 1979.
He told how two-spiked spheres then rolled out towards him and, as he passed out, he was aware of being grabbed on either side of his legs. Mr Taylor woke up in a dishevelled state 20 minutes later.
Mr Taylor, who died in 2007, was a respected war hero and teetotal churchgoer. No-one doubted that he was sincere in what he believed he had seen and throughout the rest of his life he never deviated from his story.
He told the police he had been working alone checking fences and gates at Dechmont Woods at 10:30 when he came across the spaceship in a clearing.
After the spiked objects rushed out and tried to grab hold of him, all he could remember was a strong smell of burning.
When he came to, the clearing was empty, apart from a pattern of deep regular marks on the ground. He went to his van but was so shaken he drove it into a ditch and had to stagger home in "a dazed condition".
When he got to his house he told his wife Mary he had been attacked by a "spaceship thing". Because Mr Taylor was in such a state, the police were called and officers found themselves inquiring into an assault on a forester by alien beings.
Det Con Ian Wark, the scene of crime investigator, arrived at the clearing to find a large gathering of police officers were already there.
He told the BBC he saw strange marks on the ground. There were about 32 holes, which were about 3.5 inches in diameter, as well as marks similar to those made by the type of caterpillar tracks often fitted on bulldozers.
The officer went to Mr Taylor's employer, Livingston Development Corporation, to see if the machinery they had could solve the mystery.
"After examining every piece of machinery they had up there, we did not find anything to match," he said.
The police officer said that the unusual marks on the ground were only to be found in the clearing where Mr Taylor had experienced his reported close encounter.
"These marks just arrived," Det Con Wark said. "They did not come from anywhere or go anywhere. They just arrived as though a helicopter or something had landed from the sky."
The police report from the time said the marks on the ground indicated an "object of several tons had stood there but there was nothing to show that it had been driven or towed away".
PC William Douglas wrote: "There appeared to be no rational explanation for these marks."
As part of the police investigation, Mr Taylor's ripped trousers were sent for forensic examination but this was many years before modern DNA techniques so analysis concentrated on how the damage had been done.
Police forensics said the trousers seemed to have been damaged by something hooking them and moving up.
The trousers are now in the possession of Malcolm Robinson, a Ufologist who has been investigating such cases since the Dechmont incident.
He said they were police-issue blue serge trousers and the type of rips in them did not happen by getting snagged as Mr Taylor crawled away on the ground.
Mr Robinson, who has given lectures on the incident across the UK, Holland, France and the USA and written a book on the subject, said it was one of the most incredible cases in the world.
He said it was one of very few hardcore cases that defied any explanation.
There are many theories about what actually happened to Mr Taylor. These include everything from hallucinatory berries to blackball lightning and a mirage of the planet Venus.
A medical explanation could lie in an epileptic seizure being suffered by Mr Taylor but there was no evidence of this gathered at the time.
In her police statement, his wife Mary said Mr Taylor had no history of mental illness but had contracted meningitis 14 years earlier.
She said the treatment was successful although in July of that year he had suffered a series of headaches and was admitted to the City Hospital in Edinburgh.
In his statement, Mr Taylor said that after the UFO incident he was examined by the local doctor who called at his house. The doctor suggested he should go to nearby Bangour Hospital for a check-up and x-ray.
After waiting for two hours at the hospital he got fed up and left without being examined.
Det Con Wark said he could go along with the theory about the epileptic fit. "But what about the marks on the ground?" he said.
The former police officer cannot bring himself to say he believes Mr Taylor saw an alien spaceship.
"I'd have to see it myself to believe it," he said.
But he said he interviewed Mr Taylor three times and he never changed his story.
"He believed what he saw and there was no way he would make that up," Det Con Wark said.
Forty years on the Dechmont incident has passed into legend.
Last year a UFO trail opened which takes people to the spot where a new town forestry foreman claims he saw an alien spaceship.