How TV finally dared tell of the rumours that threatened the Queen's marriage and cuckolded the Prime Minister.

It has taken American money and a British writer to finally turn them into a television watercooler moment.

The alleged liaison involving Prince Philip and an actress had been spoken about for years in polite circles, but hardly anywhere else. And the decades-long romance between the PM’s wife and a bisexual politician who befriended one of the Kray twins might have been forgotten, had it not been for Peter Morgan.

The dramatist who turned the story of Brian Clough’s disastrous flirtation with Leeds United in the 1970s into an acclaimed film is now the creative force behind The Crown, the monumental history of the Queen’s reign. Its second series began streaming on Netflix at the weekend – and its interweaving of national events with the lives of the royals has made compelling viewing.

Some of the history is well document­ed. But the divorce of Eileen Parker from her husband, best friend and equerry to Prince Philip, is a story hitherto seldom told.

In an unpermissive society in which divorce remained a source of shame, the embroilment of Philip’s chum created a climate of guilt by association towards the Duke himself and aroused fears for the future of his marriage.

The Crown does not directly accuse Philip of conducting an affair – though he is seen disappearing furtively into the huts of native women on a world tour in 1956 – but it does link him romantically with the Russian ballerina, Galina Ulanova, who was performing with the Bolshoi in London at the time. In Morgan’s telling, the Queen finds a locket with her photograph in Philip’s briefcase.

Philip’s vulnerability to such gossip was fuelled by his membership, with Mrs Parker’s husband, Mike, of the all-male Thursday Club in London’s Soho, at whose exclusive luncheons stories were shared. Chief amongst these were the exploits of the playboy Prince, whose reputation had preceded him.

In 1948, the newly-married Philip had been introduced to the film star and singer Pat Kirkwood, in her dressing room at the Hippodrome Theatre. The two were said to have dined alone that evening and to have danced until dawn at a nightclub.

Miss Kirkwood is said to have met Philip again and exchanged letters with him during the future Queen’s pregnancy with Prince Charles.

She always denied any impropriety but the rumours damaged her reputation, and when she died at a nursing home in Ilkley 10 years ago, her fourth husband, the former president of the Bradford and Bingley Building Society, Peter Knight, said that the loss of recognition and absence of any honour for what had been a stellar career, had hurt her deeply.

Yet although it has been hinted at in various biographies, the rumour about Philip only finally reached the public domain when Netflix, an American company unconstrained by British broadcasting etiquette, made The Crown. For many viewers it has come as a revelation – as has Morgan’s telling of the 30-year affair between the aristocratic Lady Dorothy Macmillan, wife of the Conservative prime minister, and the politician and author Bob Boothby, who may have been the father of her late daughter. Boothby, later ennobled by Dorothy’s cuckolded husband Harold, was a divisive figure – openly bisexual and indiscreet about meeting young men supplied by the homosexual gangster, Ronnie Kray.

Matt Smith, the former Doctor Who who plays Prince Philip in The Crown, said last week that the Duke remained “an enigma”. Asked by a dinner companion whether he had seen the first series of the show, Philip had replied simply: “Don’t be ridiculous.”