The series, which has already aired two seasons, is recasting all of its key roles for its third and fourth seasons to reflect a jump forward in narrative time.

Bonham Carter would replace actress Vanessa Kirby who played Princess Margaret in the first two seasons of the show.

According to the trade publication The Hollywood Reporter, the producers of the series are close to finalising a deal with Bonham Carter.

The producers have already announced Broadchurch star Olivia Colman will replace Claire Foy in the series' lead role, that of Queen Elizabeth II.

No announcement has been made about the actor who will replace Matt Smith as Prince Philip, though Smith has admitted in interviews he suspects he knows the actor's identity.

"I don't want to speculate too much, but he's brilliant, if it's the person I think it might be," he said. "And he's incredibly handsome as well. I've morphed into someone far better-looking than I."

Though the first seasons of The Crown focused on the early married life of the Queen and Prince Philip, the second season also explored the early married life of Princess Margaret and Anthony Armstrong-Jones (Matthew Goode).

The third season will shift the story into the 1970s, and will include Princess Margaret and Lord Snowdon's 1976 separation and 1978 divorce.

It will also introduce audiences to Camilla Shand, who met Prince Charles at polo match in 1971; the couple dated until Charles left for a naval posting in 1973.

Each season of the series has covered a little less than a decade of history; season one spanned eight years, season two spanned seven.

The series, created by Peter Morgan, launched in 2016 and takes its creative cues from previous Morgan projects, including the 2006 feature film The Queen and the 2013 stage play The Audience.