Frank Sinatra had been a huge teen idol in the 1940. He was one of the very earliest pop stars, but by the mid-1950's he had become more popular with their parents, replaced by the new wave of rock and roll stars who were led, of course, by Elvis.

His music and film career had been somewhat slowed by a year of military service which ended on March 1960, but he was still the biggest idol in the world at that time. Sinatra had no choice about hosting an Elvis special episode of his own light entertainment show on May 12.

Even though the Rat Pack legend had loudly and publicly denounced rock and roll as "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."

He also already knew that the sex symbol, who was 20 years his junior, was having an affair with his girlfriend, and later fiancée.

Elvis was filming the movie GI Blues at the time and his on and off-screen love interest was the sultry Anglo-American brunette actress and dancer, Juliet Prowse, who had been dating Sinatra since they met the previous year on the set of the movie Can Can.

Ol' Blue Eyes was so besotted he had her frequently on his TV show as a backing singer and would sing romantic numbers directly to her.

The King, meanwhile, had left Priscilla Beaulieu back in then West Germany, and was officially still dating starlet Anita Wood. However, he was already notorious for pursuing his female co-stars.

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."

Everything appeared very cordial on screen during the filming of the Frank Sinatra Timex Show: Welcome Home Elvis. Sinatra even had a go at dancing with 'the Pelvis', even though, just two years earlier, he had said of rock and roll: "It is the most brutal, ugly, degenerate, vicious form of expression it has been my displeasure to hear..."

He also made jolly jokes about how The King may not have lost any of his fame and fans during military service but he had lost his sideburns.

The pair duetted on a mash-up of Love Me Tender and Witchcraft. Although Elvis was only actually on screen for an estimated eight minutes in total, the broadcast pulled in almost 70% of the entire viewing audience.

As for the private lives and tangled relations of the two men...

Elvis and Prowse amicably went their own ways after filming finished. He continued to date Anita Wood, who along with fans, had picked up on all the gossip rags' obsession with teenage Priscilla.

Sinatra and Prowse's relationship actually intensified. She said; "Frank and I are mature people. We don't go for this teenage bit about going steady and all that jazz."

She would frequently join Sinatra when he had shows in Las Vegas. He proposed to her in 1962 but they soon separated, with her confiding to celebrity columnist Hedda Hopper: "Frank wants me to give up the business," something she had no intention of doing. Years later she added: "I was as much flattered as I was in love."