Helena Bonham Carter and Jason Watkins join cast of The Crown

Helena Bonham Carter has said she is “terrified” to be taking over from Vanessa Kirby as it was confirmed she will play Princess Margaret in the third series of The Crown.

The actress, who was previously rumoured for Netflix’s blockbuster royal drama, was officially announced for the role alongside Jason Watkins, who will play former prime minister Harold Wilson.

They join previously announced cast members Olivia Colman as Queen Elizabeth II and Tobias Menzies as Prince Philip, who are taking over from Claire Foy and Matt Smith.

Kirby was nominated for a TV Bafta for her portrayal of the Queen’s younger sister.

Bonham Carter said: “I’m not sure which I’m more terrified about – doing justice to the real Princess Margaret or following in the shoes of Vanessa Kirby’s Princess Margaret.

“The only thing I can guarantee is that I’ll be shorter (than Vanessa).”

Watkins said: “I am delighted to become part of this exceptional show. And so thrilled to be working once again with Peter Morgan. Harold Wilson is a significant and fascinating character in our history. So looking forward to bringing him to life, through a decade that transformed us culturally and politically.

“And excited to be working so closely with Olivia; and the whole team.”

Bonham Carter, 51, is known for her many film roles, including her Bafta-winning stint in The King’s Speech, as well as The Wings Of The Dove, Hamlet and the Harry Potter films.

Watkins, 51, won a Bafta for his role in mini-series The Lost Honour Of Christopher Jefferies, and has also starred in TV shows Trollied, Being Human and Dirk Gently.

The lavish biographical drama programme, created by Peter Morgan, will refresh its cast as time goes on to reflect the ageing of the characters.

It started in 1947 and ended in 1955, portraying the earlier days of the Queen’s reign for its first season, while the second covered the life of the royals from 1956 until 1963.

The Crown will return for series three in 2019.