Tom Cruise’s VERY Risky Business: Co-star claims A-lister juggled 'B*** j***' and Bible study' on set of cult classic movie AND had an affair with costar Rebecca De Mornay

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Tom Cruise once skillfully juggled 'b*** j*** and Bible study' on the set of cult movie Risky Business, according to one of his former co-stars.

Curtis Armstrong made the revelations about the young Cruise in his new tell-all book, Revenge of the Nerd.

Then just 19 and relatively unknown, it was the last movie he was just 'Tom' before becoming Tom Cruise the international movie star we know today, according to Armstrong, who was 28 when he starred across from him in the eighties hit.

Even then, Cruise portrayed himself as a straight laced, devout young actor, who would spend most evenings reading the Bible before bed.

But Armstrong claims that Cruise also found some slightly less wholesome activities to occupy his free time. 

Tom Cruise once skillfully juggled 'b*** j*** and Bible study' on the set of cult movie Risky Business, according to one of his former co-stars

Hot stuff: Armstrong made the claim in his new tell-all book Revenge of the Nerd. 'It's no secret that Tom engaged in an intense affair during the shooting with De Mornay,' he added (pictured are De Mornay and Cruise in a steamy sex scene)

He described how he had returned late one night to find 'three or four young girls - late teens, I suspect' lined up in the hall outside of then 19-year-old Cruise's room.

'I remember thinking, 'Tom's going to be really upset if these hot girls interfere with his Bible reading'', he wrote.

'So I asked them, with all the stern gravitas of my 28 years, if there was something I could do to help them.

'They just stared at me and at that moment, Tom's door opened and another girl came out adjusting her hair and taking off down the hall, while the first girl in line slipped into Tom's room.

'This was a young man who knew something about time management and understood how to successful juggle Bible study with b*** j***.'

Close ties: Tom Cruise had a romance with Risky Business co-star Rebecca De Mornay. This comes from Curtis Armstrong, their co-star in the 1983 movie

Naughty business: There is a very graphic sex scene in the movie with the stars

Armstrong, who plays Miles in the 1983 movie, said he was surprised by the later rumors surrounding Cruise's sexuality as 'there was no question which side of that particular fence Tom stood on' during Risky Business.

When he wasn't invited girls back to his room, according to Armstrong, he was engaged in an 'intense affair' with the movie's leading lady Rebecca De Mornay, who played Lana.

At the time the beautiful blonde was dating actor Harry Dean Stanton, who is 33 years older than herself, the book alleged. 

Armstrong's Revenge of the Nerd book

Tom was not happy with Dean, Curtis stated in his book.

Curtis wrote: 'I suspect that most of Harry Dean's great qualities were lost on Tom who, I think, was beginning to regard him as a guest overstaying his welcome.'

Tom and Rebecca seemed to continue to date after the film wrapped. In 1985 they were spotted together at a screening for the movie The Breakfast Club. '

Despite his busy social calendar, Armstrong said that Cruise, who would later convert to Scientology, was devoutly religious.

'He self-identified as a born-again Christian and the rumor was he had actually considered shepherding souls for a living,' Armstrong, who went onto star in Revenge of the Nerds, wrote. 'I could believe it. Away from the set, initially, Tom made straight arrows look like corkscrews.

'I would ask him at the end of the day if he would like to join us at the bar for a drink. 'No,' I recall him saying, 'Got an early call tomorrow. Got to work out still, study my lines. And then I like to read the Bible a little before bed.'

These days: Rebecca, now 57, and Tom, now 54, still look great

The other man: At the time the beautiful blonde was dating actor Harry Dean Stanton, who was 33 years older than she; seen here in 2014. He is now 90-years-old

One of the things that first struck Armstrong on meeting Cruise was how polished and neat he was.

'He appeared so … clean,' he said, adding that Cruise's room was also scrupulously today.

Armstrong revealed that, while Cruise was relatively unknown at the time, he quickly became aware the the up-and-coming actor 'possessed an absolute and voracious ambition... that suggested that anyone who stood in his way, or underestimated him in any way, did so at his or her own peril.'

In spite of everything, Armstrong says it was 'difficult not to like him.'

They couldn't let go: Tom and Rebecca seemed to continue to date after the film wrapped. In 1985 they were spotted together at a screening for the movie The Breakfast Club 

His first wife: In 1987 Tom wed Mimi Rogers but the two divorced in 1990; she is now 61. They are seen here in 1989

He also described Cruise's close relationship with a young Sean Penn.

The pair would hang out together and would often be found 'in bed or lounging in underwear' after Penn came to visit.

'It looked like a Calvin Klein ad, he added.

Risky Business follows Joel Goodsen (Cruise) who hires Lana (De Mornay) for a night of delight when his parents go on holiday.

However, the morning after Joel is shocked at Lana's 'bill' and resorts to turning his house into a brothel to raise the money fast.

In 1987 Tom wed Mimi Rogers but the two divorced in 1990; she is now 61.

His wives after her were Nicole Kidman and Katie Holmes.

The actor appears to be single since his split from Holmes who he has daughter Suri with.

De Mornay's manager Chuck Binder declined to comment. 

DailyMail.com has reached out to Cruise's representatives for comment.