But there were to be no romantic fireworks. Loren had already turned down Frank Sinatra on the set of The Pride and the Passion, calling him an “Italian S.O.B.”, and dumped Cary Grant to marry Carlo Ponti.

Heston, meanwhile, was happily married to his photographer wife and had no plans to become a tabloid fixture. He gallantly admitted that Loren was a “double helping of woman”, but his true fervour was for acting. “Doing the work, it’s as good as sex!” he declared. He prepared by poring over 11th-century history books and consulting scholars about the real El Cid. He shed pounds learning to ride and fence, even cutting his forehead with some errant swordwork.

Heston, a strangely anxious old- school icon, was most worried about El Cid’s triumphant march through Valencia, but on the day the scene worked brilliantly. Surrounded by two thousand extras, cheering “Cid, Cid”, no acting was required. “I know what it is to take a city,” he said. “It is sex to the power of ten.”

He found it harder to play the warrior hero in real life. At a dinner with Rita Hayworth, he watched as she was relentessly abused by her then husband, James Hill. “The single most embarrassing evening of my life,” Heston called it. He wanted to “slug” Hill, but said that he was waiting for him to hit Hayworth. Years later, he admitted: “I wish I hadn’t waited.”

As for Loren, she was quite the Latin handful. She kept her co-stars waiting and refused to wear any ageing make-up for the later scenes. She badgered the cameraman for more flattering light and insisted on wearing a majestic but incongruous pointy bra. On her final day of filming, she slipped and broke her shoulder, forcing Heston to act his death scene — “the most important close-up in the film” — without her kneeling beside him.

El Cid, Monday, BBC Two, 1.50pm

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