The blunt words Prince Charles's top staffer gave him before admitting bombshell cheating revelations

In an interview that stopped the world, Prince Charles finally admitted he had cheated on then wife Princess Diana, fuelling fans and critics alike with a wave of satisfaction after years of speculation.

The 1994 documentary, though largely sympathetic, captured the polarising prince onscreen, sitting stiffly on a sofa at his Gloucestershire estate, responding point-blank to well-known British journalist Johnathan Dimblely's questions of infidelity.

In a gripping sentence, the Prince of Wales admitted to a long-rumoured fact, claiming he'd been faithful to his wife, "until it became irretrievably broken down, us both having tried."

The bombshell interview irreversibly changed the public's perception of the prince, with many questioning whether he was a suitable heir to the throne.

But moments before sitting down with the media, his then press secretary Dickie Arbiter issued him a warning in four blunt words: "you cannot deny anything."

Discussing the moment on the new Channel 5 documentary, 'Charles and Camilla: King and Queen in Waiting', Arbiter explained: "I warned them at the time it would have to be warts and all."

"You cannot leave anything out. And nothing was left out," he confirmed. 

Prince Charles bared his soul in the now infamous interview, discussing his personal life in unprecedented lengths and redefining the standard to which the British Royal family would share with the press.

Commenting on the love-triangle that makes the Brangelina-Jennifer Anniston affair a mere footnote in history, Charles claimed of his then ex-girlfriend, Camilla Parker-Bowles, that she was "a great friend" and was among a "large number of friends that I'm terribly lucky to have."

"So many friends who I think are wonderful, and make a huge difference to my life which would be intolerable otherwise. She has been a friend for a very long time," the Prince said.

Arbiter claimed the ensuing negative press the Prince received had made him "very upset", typifying the coverage as "very vicious."

Diana followed the confession with an hour-long interview a year later with Panorama, famously claiming, "there were three of us in this marriage, so it was a bit crowded."

The late princess explained she had been aware of the affair but "wasn't in a position to do anything about it".

Arbiter said following the interview, Diana had personally expressed to him she'd regretted it.

Since it's debut, Channel 5's documentary 'Charles and Camilla: King and Queen in waiting' has revealed a series of revelations about the Duke and Duchess of Cornwall's relationship.

Commentator Daisy McAndrew suggested the Prince of Wales has become "happier" since his second marriage.

"I think it's very clear when you look at Charles and Camilla over the last 15 years what a difference she has made to his persona, to his outlook, to his demeanour," she said.

"He's just clearly a much happier person now. He's relaxed a bit."