Elvis went on Frank Sinatra's show and slept with his girlfriend

Frank Sinatra and Elvis Presley were both idolised by millions of women – and both happily enjoyed numerous affairs throughout their careers (and marriages). But what happened when one was sleeping with the girlfriend of the other? Old Blue Eyes has an entire evening devoted to his career and his TV appearances tonight on BBC2. As well as his radio, record, movie and Rat Pack fame, he was a major TV personality, with his own light entertainment show in the late 1950s and early 1960s, just when Elvis was the biggest and hottest star in the world. On May 12, 1960, the crooner celebrated The King's March 5 return from military service with a special edition of The Frank Sinatra Show.

Elvis fit it in between his busy filming schedule for new movie GI Blues. The two men were all smiles, playing up their rivalry, bantering and even performing medleys of each other's songs – despite everything the host had said about his guest in the past, and everything that was going on behind the scenes. During the show, Sinatra even had a go at dancing with Elvis, even though, just two years earlier, he had said of rock 'n roll: "It is the most brutal, ugly, degenerate, vicious form of expression it has been my displeasure to hear... It fosters almost totally negative and destructive reactions in young people. It smells phony and false. "It is sung, played and written for the most part by cretinous goons and by means of its almost imbecilic reiterations and sly, lewd—in plain fact, dirty—lyrics, and as I said before, it manages to be the martial music of every sideburned delinquent on the face of the earth … this rancid-smelling aphrodisiac I deplore." WATCH ELVIS ON THE FRANK SINATRA SHOW BELOW.

Behind the scenes, Elvis was having a passionate sexual affair with Juliet Prowse, even though he had just left future wife Priscilla Beaulieu behind in Germany and was still officially dating starlet Anita Wood in the US. Actress and dancer Prowse had been with Sinatra since they met the previous year on the set of the musical Can-Can. The crooner was so instantly smitten that he had her guest on his national TV show as a backing singer. He would even sing some numbers directly to her. However, in April 1960, Prowse started filming GI Blues with Elvis, playing nightclub dancer Lili. As so often happened, The King soon started an affair with his beautiful co-star. DON'T MISS

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Prowse said: "Elvis and I had an affair... We had a sexual attraction like two healthy young people, but he was already a victim of his fans. We always met in his room and never went out." Extraordinarily, she also openly declared at the time that Sinatra knew about it. Prowse, who was 24 at the time, added: "Frank and I are mature people. We don't go for this teenage bit about going steady and all that jazz." In fact, their relationship only intensified after her fling with Elvis. She would also join Sinatra when he had engagements in Las Vegas and he proposed to her in 1962.
• Elvis was so turned on in classic scene you can see 'Little Elvis' However, it soon burned out, with Prowse reportedly wanting to focus on her own career. She later admitted: "I was as much flattered as I was in love. He was a complex person, and after a few drinks he could be very difficult." Sinatra, meanwhile, became friends with Elvis, as their own careers started to overlap more and more in the late 1960s and early 1970s with both headlining lucrative residencies in Las Vegas. He even made a desperate call to The King begging him to change his life before it was too late, and relayed his worries to their mutual friend Tom Jones.

The three stars had become friends when they all headlined their own shows in the casino mecca. Years later, Jones' publicity man, friend and journalist Chris Hitchens revealed a candid conversation where Sinatra confessed he had tried to save The King. Hitchens said: "Tom Jones and I met up for a drink with him in New York and he told us that he had just been on the phone to Elvis." The King had been admitted to hospital in August 1975, with liver problems exacerbated by his heavy drug use. Friends and family were starting to worry about him, which prompted an extraordinary intervention from his fellow star.