Tobias Menzies thinks he was third choice to play Prince Philip in 'The Crown'

He said: "Initially I think they went after Mark Strong, then Paul Bettany, and then it came back around to me.

"I did one audition where I read 10 pages with Colly (Olivia) and two weeks later I found out. Weirdly, for the size of the show it was relatively straightforward."

Helena Bonham Carter, who plays Princess Margaret, has spoken of how she spoke with the late princess' former lover, Roddy Llewellyn, and some of her ladies-in-waiting as part of her research into the role, but Tobias wasn't so lucky.

He told the Sunday Times magazine: "I sadly didn't have anyone on the inside. Helena is a bit more of a ninja than me.

"I read quite a bit and a lot of it began technically. The voice is very important -- and the gestures... He's very pointy.

"Wanting to be like him but not have it become a caricature is quite a tough pitch. If you become too vocally mannered, then it's hard for the viewer to get into the story."

The former 'Game of Thrones' star had to do a lot of research into the role as he had grown up in a household where his mother held "pretty anti" views about the monarchy.

He said: "She was pretty anti the royal family. She would actively never put on the Queen's speech, so, as a result, prior to doing 'The Crown', they weren't on my radar. I didn't read about them or pay attention to them -- they were just part of the furniture.

"There's definitely been a learning curve in that, with this job, I'm looking at them for the first time."