Would lie for hours staring down and documenting the sex lives of guests

After buying a motel he installed vents in the ceilings of many of the rooms

Gerald Foos' (pictured) story is so compelling it has been chronicled in a forthcoming book

Had movie mogul Steven Spielberg stumbled across the Manor House Motel, sandwiched between fast-food outlets and car repair shops on the gritty main street of a nondescript U.S. town, chances are he would have hurried straight past.

Inside, service was patchy. The unprepossessing owner, while polite and solicitous, often took some time coming to reception for a night-time request and was invariably a little out of breath.

The rooms were unremarkable, save for one particular feature: some slightly unusual vents, 6in x 14in louvred screens, prominently located in the ceiling of the bedrooms.

Had the guests been able to investigate them closely, however, they might have been in for a terrible shock: a pair of eyes — sometimes two pairs of eyes — staring down intently at them. And the man doing the staring — owner Gerald Foos — has just been exposed as history’s most determined and dedicated Peeping Tom.

His story is so compelling it has been chronicled in a forthcoming book, the rights of which have been snapped up by Steven Spielberg to be made into a film directed by the British-born, Oscar-winning Sam Mendes, former husband of actress Kate Winslet.

The extraordinary tale — a chilling insight into what drives an otherwise respectable, married, father-of-two to sink to such depths — will, with Spielberg’s interpretation, doubtless have cinema audiences riveted and appalled.

When Foos, a former U.S. Navy underwater demolition expert, bought the single-storey, green-and-white-painted motel in the Denver, Colorado, suburb of Aurora in 1969, he wrote in his journal that it was ‘the fulfilment and realisation of a dream that has constantly occupied my mind and being’.

But it wasn’t a dream of entering the hotel trade.

‘Finally, I will be able to satisfy my constant yearning and uncontrollable desire to peer into other people’s lives. My voyeuristic urges will now be placed into effect on a plane higher than anyone else has contemplated.’

He wasn’t exaggerating. Not for him the simple, if deviant, pleasures of watching a neighbour slip into her nightie. His voyeurism was on an industrial scale.

Having bought the 21-room motel, Foos ingeniously converted it into a pervert’s paradise and spent the next 26 years spying on his guests’ sexual behaviour.

Every night — and day if he felt they looked the type — he would creep up into the motel’s attic and peer for hours down through the fake air vents installed in the ceilings of more than a dozen rooms.

He was never caught and we only know his astonishing story because he couldn’t resist seeking the acclaim he thought he deserved.

In 1980, he wrote to Gay Talese, a celebrated New York writer and chronicler of exotic sexual behaviour, to boast: ‘Sexually, I have witnessed, observed and studied the best first-hand, unrehearsed, non-laboratory sex between couples, and most other conceivable sex deviations during these past 15 years.’

Finally, I will be able to satisfy my constant yearning and uncontrollable desire to peer into other people’s lives. Gerald Foos

Foos subsequently revealed all to Talese, who wrote about his exploits in the New Yorker magazine and is about to publish a book.

Experts say voyeurism is all about secrecy so its practitioners are prone to lying. However, Talese knows Foos was telling the truth because he invited the writer to see his twisted operation for himself.

Talese agreed and he recalls arriving in Denver in 1980, where he was met by a slightly overweight, 6ft tall man in his mid-40s who wore spectacles and ‘projected a friendly expression befitting an innkeeper’.

As they drove to the motel, Foos described how his kind, hard-working parents had been German-American farmers who never discussed sex or seemed interested in it.

His mother always dressed in the privacy of her closet, so her sexually curious son started spying instead on his aunt, who lived on a neighbouring farm.

From the age of nine, he spent the next six years spending an hour most evenings peering furtively through her window and watching her walk naked around her bedroom.

He was never caught, clearly encouraging him to widen his voyeuristic ambitions. Quite how extensive they became was made clear to Talese that night as soon as Foos’s live-in mother-in-law had gone to bed.

When Foos, a former U.S. Navy underwater demolition expert, bought the single-storey, green-and-white-painted motel in the Denver, Colorado, suburb of Aurora in 1969, he wrote in his journal that it was ‘the fulfilment and realisation of a dream that has constantly occupied my mind and being’

Like the children, she didn’t know his secret. His wife, however — a nurse named Donna — most certainly did. She was an enthusiastic collaborator and had even helped Foos install his secret ‘peep holes’.

She would lie on each bed and, looking up, help him adjust the angle of each vent’s louvres so he couldn’t be seen by his victims.

When he was ‘on the job’, she would bring him snacks.

Sometimes she would lie next to him to watch, too, and occasionally they would have sex up there on what he called his ‘viewing platform’.

As Talese discovered, this was reached from the utility room via a ladder that led up to the attic. There, Foos had laid down a thickly carpeted catwalk extending over the ceiling of all 21 guest rooms.

Filmmaker Steven Spielberg has bought the rights to Foos' book, for a film directed by Oscar-winner Sam Mendes

An attractive young couple — better-looking guests were always given the ones with spy vents — was occupying one of the rooms and Foos stopped at their vent.

The two men peered in and found they were in luck. Talese almost gave the game away after his necktie dangled through the vent just yards above the woman’s head, but the couple didn’t look up during their lovemaking.

Foos admitted his covert peeking gave him a thrilling feeling of power. He was doing nothing morally wrong, he argued, unconvincingly to Talese, if his guests didn’t know they were being watched.

Foos didn’t just watch, he recorded meticulously. Like all addicts, voyeurs try to rationalise their addictions and Foos insisted he was engaged in a serious scientific study akin to that of the famous sex researcher Alfred Kinsey.

He hailed his dingy motel ‘the finest laboratory in the world for observing people in their natural state’, logging what they did in his ‘Voyeur’s Journal’ in such detail that he would even visit their rooms when they were out to double check a woman’s bra size.

Any sexual activity would be timed and, combined with their other behaviour, appraised by Foos, who would write his conclusions about the state of their relationship.

In 1973, for example, he catalogued 184 male and 33 female orgasms from 296 sexual acts, noting the sexual positions. Only 3 per cent of couples didn’t have sex, while 12 per cent were ‘highly sexed’.

Sex therapists I spoke to are enthralled by Gerald Foos. None could think of a more extreme case of voyeurism, which is one of the more common fetishes or paraphilic disorders — a technical term for sexual perversions.

Ninety per cent of voyeurs are men, and women who do it tend to be severely mentally ill.

The compulsion usually starts before the age of 15 and becomes progressively stronger and more extreme.

Experts say that a feeling of having secret power over people is a crucial part of its attraction. Dr John O’Neill, director of the Menninger sex addiction clinic in Texas, dismisses as self-delusion Foos’s attempts to intellectualise his peeping and his insistence he never hurt anyone.

‘It’s all about sexual gratification. Voyeurism is designed to infringe on other people’s space, and people feel incredibly violated when they discover they have been watched,’ he says.

Foos’s obsessive documenting of what he saw as simply a glorified urge is common among fetishists, who like to keep mementos.

Foos didn’t just watch, he recorded meticulously. Like all addicts, voyeurs try to rationalise their addictions and Foos insisted he was engaged in a serious scientific study akin to that of the famous sex researcher Alfred Kinsey. Pictured, the patch of land where the Manor House Motel once stood

What causes someone to become a voyeur in the first place is invariably rooted in a childhood sexual experience. It could have included abuse, but is always likely to have been abnormal.

Dr Stephen Betchen, a sex therapist in New Jersey, says even trivial events can lead to paraphilia — he once treated a man who developed a foot fetish because his mother used to walk around semi-naked wearing stiletto heels.

He believes Foos’s compulsive voyeurism started not with his infatuation with his aunt, but with his mother’s insistence on undressing only in her closet. ‘Voyeurism is about hiding and the powerlessness of childhood. The mystery of his mother going in that closet and the fact he couldn’t see her naked, that would have been titillating and frustrating,’ he says.

Sexually, I have witnessed, observed and studied the best first-hand, unrehearsed, non-laboratory sex between couples, and most other conceivable sex deviations during these past 15 years. Gerald Foos

Yet that pales into insignificance compared with some of the behaviour Foos observed as an adult, such as the trio — two neatly dressed men and a woman — who turned up within months of him opening for business and asked for a single room.

Foos rushed up to the attic to find the woman’s husband photographing her as she had sex with the other man. ‘Then they all lay quietly on the bed and relaxed, discussing vacuum cleaner sales,’ Foos wrote drily. He later discovered the couple owned a cleaner company and the other man was their sales rep.

Other ‘highlights’ included an obese gay man who made his lover dress up as a sheep.

Foos almost gave himself away several times. Once, he saw a guest’s dog foul a room’s carpet and — furious when they didn’t own up when they checked out — he frogmarched them back to the room and pointed to the stain.

Dogs, he admitted, were an unforeseen hazard as they could detect his presence and would often stare at the vent and bark.

For all his caution, he did sometimes take risks. On one occasion, he was desperate to see a particular woman naked, but the room was shrouded in darkness. He quickly parked his car outside her room with the headlights glaring in, and went back to his post.

Foos became increasingly depressed by the behaviour of his guests, complaining about their sloppy eating habits, dishonesty and continual arguments.

Talese, who was sent hundreds of pages from Foos’s journal, thought the pressure of his voyeurism was bringing him close to a nervous breakdown.

After his wife died, he married another woman — Anita — who, oddly, was even more enthusiastic about his voyeurism. He bought a second motel nearby and installed fake vents there, too.

Foos sold both motels in 1995 — having developed arthritis that made it too painful to negotiate the attic ladder — and finally gave Talese permission to write about him in 2013, coincidentally the same year that his daughter, Natalie, died, aged 53.

Now aged 83, not only has he escaped prosecution because the offences happened too long ago, but he has been paid by Talese’s publisher for the use of his journal.

Anita, his wife and fellow voyeur, is still alive, but Foos is estranged from his son, Mark, whose views on his father’s unedifying obsession are not known.

Revealing himself to wider scrutiny for the first time, Foos admits he is nervous, explaining that he fears some may not be bowled over by his decades of ‘devoted research’.

‘I think the book will create a real situation, let’s put it that way,’ he says. ‘I don’t know if I’m ready for anything, to be honest with you. I’m just a poor soul.’