Safety came first for Robert Redford on the set of his sweeping romantic drama.

The actor allegedly wore “two athletic supporters” to film his love scene with Barbra Streisand for their 1973 film “The Way We Were.”

The claim was made by author Robert Hofler in his book published on Tuesday titled “The Way They Were: How Epic Battles and Bruised Egos Brought a Classic Hollywood Love Story to the Screen.”

The book, timed to the 50th anniversary of the film’s release, explores how the instant classic was “a nightmare to make, with a difficult cast, a jumbled plot about mismatched partners, countless delays and rewrites, on-set tensions between everyone involved, difficulties at every step of the production, the skyrocketing demands of Ms. Streisand, a leading man who happily ditched premieres on both coasts and mixed critical reviews.”

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Reps for Redford, 86, and Streisand, 80, did not immediately respond to Fox News Digital’s request for comment. The U.K.’s DailyMail published the original excerpt on Wednesday. Fox News Digital obtained a copy of the book. 

Hofler claimed that Redford was reluctant to work alongside the “Funny Girl” star, and when it was time to get in bed with Streisand, the Hollywood heartthrob did not take any chances. He allegedly doubled up on the jock straps “to protect himself in more ways than one,” while Streisand “chose to don a bikini.”

“Redford was a happily married family man with four children when he signed to do ‘The Way We Were,'” Hofler explained in his book.

“It was a pretty G-rated scene,” assistant director Michael Britton shared.

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Producer Ray Stark cautioned that he did not want “a heavily shadowed nude scene.” However, the film was going to be rated PG, and he had already deleted a “f—” from the script to avoid “a dreaded R rating.” This would ensure “the largest audience possible” at the box office.

The intimate scene was supposed to be a simple one to film on a closed set. However, Britton said, “there were a lot of takes.” At one point, Redford looked at director Sydney Pollack, implying he had enough. Redford would later joke to a Newsweek reporter that the only thing he wore on set for the scene was “Aramis,” the Estée Lauder fragrance for men.

“Redford tended to do his best in the first take, maybe the second, rarely the third, never the fourth,” Hofler wrote. “From there, he tended to lose energy and concentration.”

Eventually, Redford “lost patience and Pollack had no choice but to inform his female star, ‘I think we’ve got it.'” Editor John Burnett was said to be “amazed at how much footage he had to work with to put together the simple lovemaking scene.”

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However, there may have been another reason why Redford was wary about the love scene. The book alleged Streisand was “infatuated” and “mesmerized” with her co-star, who was playing a “Ken doll,” as he described.

“Barbra Streisand was a star who reportedly had affairs with many of her leading men,” claimed an unnamed member from the film set.

During their second love scene, Redford allegedly refused to say the line, “It will be better this time,” because he felt people would assume he was not a good lover.

“Redford was never bad in bed” so his character couldn’t be either, Hofler noted.

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The book claimed Redford had concerns about his leading lady from the start. The actor told Pollack he did not believe Streisand was “a serious actress” because she “had never been tested.”

“Her reputation is as a very controlling person,” said Redford, as quoted in the book. “She will direct herself. It’ll never work… She’s not going to sing, is she? I don’t want her to sing in the middle of the movie.”

Streisand went on to sing the film’s iconic theme song, “The Way We Were.”

It took eight months of “incessant wooing” from Pollack for Redford to finally sign on. Ryan O’Neal was at one point another name being considered for the film.

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On set, it was easy to see that Streisand “had a massive crush on Bob,” but the two could not be more different.

“Barbra wanted precision; Redford, spontaneity,” said Pollack. “Barbra likes lengthy rehearsals and multiple takes. Redford is better in his early takes. After that, he just gets bored.”

Still, there was no denying that for their first reading, it was like a “lightning bolt” went off in the room.

There was one thing the stars had in common. The book claimed they both preferred having the left side of their faces to be on camera. Cinematographer Harry Stradling Jr. claimed that during scenes shot in New York City, they erected canopies everywhere to block the light from hitting Streisand’s face because her nose looked “terrible.” As for Redford, he did not like showing the three moles on the right side of his face.

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The film became a hit and a sequel was even discussed. However, Redford shot down the possibility. The actor said he never had any interest in making a second part, “but Barbra did.”