Matt Smith admitted it's difficult for 'Doctor Who' to not get caught up in its own "mythology".
Matt Smith
The 35-year-old actor played the 11th incarnation of the Time Lord, and he has opened up about how hard it can be for such a show to stay fresh over a long period of time, compared to dramas rooted in reality.
Speaking to Variety, he explained: "You're not having to invent too much and that can become a problem, because the great danger of science fiction is if you get caught up in your own mythology, it's tricky.
"We found it on 'Who'. It's a tricky thing. You've got to be very, very diligent about it all."
The star - who has finished two seasons playing Prince Philip' on 'The Crown' - admitted the period drama is set up in a way that allows it to avoid any pitfalls.
He said: "Had it been six seasons [on 'The Crown'], I might not have done it. I don't even want to do six seasons of anything really. Look, never say never, but I did four with Doctor Who and it's tough.
"What shows do you think have been brilliant over five seasons? I think 'Breaking Bad' did it. 'The Sopranos' ... that's the greatest. 'Game of Thrones'... Hopefully that's why 'The Crown' has a chance, I think, because there's a different kind of setup.
"You've got new actors coming in that are going to be fresh and that's such a good thing. And also it's rooted in history."
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