It is the hit TV show about a family we think we know.

But as the next series of The Crown gets under way, the controversy only seems to be growing about the way its history is being depicted. Stars gathered on the red carpet for the premiere of the first episode at the Curzon Mayfair in London last night.

The third series of the long-running historical drama, which follows the reign of Elizabeth II, is set to take a sharper look at the lives of the royals, and what may have gone on behind closed doors when the Queen was young.

HeraldScotland: Camley's Cartoon: Controversy over The Crown.Camley's Cartoon: Controversy over The Crown.

The new series charts the period between 1964 and 1977, dramatising the years between Harold Wilson’s election as Labour prime minister until the Queen’s Silver Jubilee.

And it has already raised eyebrows amid reports of a storyline hinting that the Queen may have been more than friends with her horse training manager, Lord Porchester.

It also explores more sensitive episodes, including Prince Charles’ early friendship with Camilla Shand, now the Duchess of Cornwall, and his first meetings with Diana Spencer.

The third series sees Olivia Colman take over the role of the Queen from Claire Foy, while Tobias Menzies replaces Matt Smith as the Duke of Edinburgh. The Queen’s former press secretary has rubbished the affair storyline, branding it “absolute nonsense”. Dickie Arbiter told Sky News that rumours of an affair between the Queen and “Porchie” had “been washing around for decades” but had always been false.

He said: “All sorts of people have written about it and made allegations, innuendos, suggestions – there’s nothing to it.” The episode in question shows the friends, who in real life shared a deep love for horses and horseracing, getting particularly close, which sparks the jealousy of Prince Philip. Mr Arbiter added: “I don’t think a lot of people do believe it. They say, ‘The Queen – an affair? What absolute nonsense’.”

Helena Bonham Carter succeeds Vanessa Kirby as Princess Margaret and Josh O’Connor stars as Prince Charles. From the red carpet, Bonham Carter said of truly knowing the inner workings of Britain’s first family: “This is all projection. It’s very difficult.

The whole point about The Crown is a lot of famous people we know nothing about. “It’s about the royal family and we ultimately know very little about them. It’s not The Crown, I call it The Conjecture. It’s a massive conjecture.” Jason Watkins, who plays Harold Wilson, said it was “very difficult” to film an episode depicting the Aberfan disaster following the death of his daughter eight years ago.

The actor, who is appearing for the first time in the lavish Netflix drama, and his wife, Clara, lost their two-year-old daughter, Maude, in 2011 due to sepsis. One episode in the third series of The Crown includes scenes based on the 1966 Aberfan coal-tip disaster, in which 144 people died, 116 of them schoolchildren.

Watkins told ITV’s Lorraine: “It’s an incredibly moving film – each episode is a film in itself – and we filmed not far from Aberfan, and the care and attention that was taken by everyone in production... “And people probably know I lost a child – me and my wife Clara lost our Maude in 2011, so to go and have an episode about the loss of a child was very difficult and, above anything else, I wanted to make it in the right way.”

He said the episode, the third of the 10-part series, “remembers that particular, that terrible tragedy”, and added: “I’m very proud to be part of that, no matter how difficult it was.” Watkins, who is new to the cast of The Crown, is best known for winning a Bafta for playing the lead in The Lost Honour Of Christopher Jefferies and Tim Ifield in Line Of Duty.

He added: “Harold Wilson was a working-class boy, grammar school, did very well, got himself to Oxford and then became prime minister.

“He was a socialist, very much championing the poor and the underprivileged.

“His father was made redundant when he was young – I think that stayed with him, so he had a kind of social agenda, perhaps.

“And you’d think that him and the figurehead of the establishment wouldn’t necessarily get on but they formed a very unlikely friendship which spanned many years, which is touching and is touched upon in the many scenes I have with her.”