Russell T Davies explains why Doctor Who is the hardest show on TV to write

"I do think the hardest show to write on television is Doctor Who," he said. "I've been there obviously and truly it's hard to write because the Doctor is a billion times cleverer than the writer, he understands art and science and the cosmos and so on, he gets everything."

He added: "The danger with Doctor Who is he walks in the door and solves the entire plot in three minutes – as a writer you have to spin plates and tap dance and juggle to stop that happening, it makes it very very hard to write.

"Let alone the fact that he arrived in a great big machine that's the most powerful object in the universe, it travels in time and is invulnerable! It's hard to worry for the Doctor when you put it like that, where the lead character starts to be so clever they're outstripping the writer!"

And he went on to highlight a number of other popular characters that fit into a similar category. "That's Jane Tennison in Prime Suspect, I think that's [Fitz in] Cracker, and Poirot and Mrs Marple, they're cleverer than anyone else in the room," he said.

"And it doesn't have to be an intellectual cleverness, Del Boy is essentially the cleverest person in the room while being an idiot, while his schemes are doomed to fail, nonetheless we would all like to be as inventive as Del Boy, as gregarious as Del Boy, as loved as Del Boy.

"That's a brilliant brilliant man, I don't mean intellectually brilliant, it doesn't have to be Doctor Who or Sherlock, it can be Del Boy... it's keeping your standards up and it's not treating your characters as dumb, not having them say dumb things."

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