'The Crown': Helena Bonham Carter, Jason Watkins confirmed for Season 3

May 3 (UPI) -- The Crown is adding Helena Bonham Carter and Jason Watkins to Season 3.

The Netflix series confirmed Thursday on Twitter the 51-year-old British actress and Watkins, also 51, will join the show, which follows the reign of Queen Elizabeth II.

Carter will play Elizabeth's sister, Princess Margaret. Vanessa Kirby portrayed a younger version of the princess in Seasons 1 and 2 of The Crown.

"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," Carter said in a statement. "The only thing I can guarantee is that I'll be shorter than Vanessa."

Watkins will play Harold Wilson, who served as British prime minister from 1964 to 1970 and from 1974 to 1976.

"I am delighted to become part of this exceptional show," Watkins said. "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 [Coleman] and the whole team."

Watkins, who is known for the British series Being Human, Trollied and W1A, teased news of his casting earlier on Twitter.

"I've been cast in such an exciting project. I've had to keep it to myself for 2 months. It's being announced this afternoon," the actor wrote.

Claire Foy and Matt Smith played Elizabeth and Prince Philip in Seasons 1 and 2 of The Crown, with Olivia Coleman and Tobias Menzies to take over in Season 3. Smith supported Foy in an interview in April following controversy about their pay disparity.