King Charles reportedly refused to let The Crown's Dominic West quit the Prince's Trust over his role in the Netflix series.
Dominic, 53, plays Prince Charles in the show and said he initially thought he should step down as ambassador from the King's charity.
However, Charles, 73, wasn't having any of it, according to the actor.
Dominic said his offer to quit was refused in a letter from the monarch's private secretary with the royal reportedly saying: "You do what you like, you’re an actor, it’s nothing to do with us".
The actor added: "I think that’s probably how [Charles] regards it. I’ve been in line to shake his hand a few times –and it’s fascinating.
"It’s very useful to meet the character you’re playing," he told Radio Times.
Season five of the controversial drama, which arrives on Netflix on November 9, chronicles the breakdown of Charles’s marriage to Princess Diana, played by Australian actress Elizabeth Debicki.
The leaked 'tampongate' conversation Charles had with Camilla, who is played by Olivia Williams in the series, will be included in the series.
The now-King’s infamous phone call with the now-Queen Consort in 1989 was recorded by an amateur radio fan, who claimed to have come across their private conversation while switching between audio channels.
A transcript of a nocturnal conversation between Charles and Camilla was published just a month after the the father-of-two and Princess Diana announced their official split.
In it, Charles could be heard telling Camilla he longed to be a tampon so he could "live inside" her.
Recorded when the then-Prince and Princess of Wales were still married, the six-minute conversation was branded "sick" by William and Harry's mum.
The transcript caused ructions within the Royal Family as it exposed the relationship between the then-Prince and Camilla, who at the time was married to Brigadier Andrew Parker Bowles.
However, Dominic said: "I never really thought about it at the time, but the research showed me how badly Camilla was treated."
While conceding he, "like most people" thought the discussion was "embarrassing", the actor reckons it was an "intensely personal conversation" that should never have been up for public consumption.
However Josh O'Connor, who played a young Prince Charles in series three and four of the show, refused to film the phone call.
He told SiriusXM in 2020: "When they offered me the role, one of my first questions was – I say questions, I think it was pretty much a statement – 'We are not doing the tampon phone call'.
"[The Crown] was my one chance for my parents to see something [I've acted in] with no shame and there's no way I was going to scuttle that by talking about tampons on Netflix."
Series five of The Crown lands on Netflix on November 9.
