Steven Moffat offered the role of Doctor Who to a black actor before Peter Capaldi took on the job.
The 54-year-old executive producer and lead writer of the BBC One sci-fi programme has admitted he initially had his eye on someone else to play the titular role before he dished it out to the 58-year-old star in 2013.
He said: "Two non-white leads would be amazing. In fact, a lot of people would barely notice. I certainly don't think there's ever been a problem with making the Doctor black, which is why it should happen one day.
"Sometimes the nature of a particular show - historical dramas, for instance - makes diversity more of a challenge, but 'Doctor Who' has absolutely nowhere to hide on this."
Pearl Mackie - whose family originate from the West Indies - was recently cast as the Doctor's new companion following the departure of Jenna Coleman.
On their decision to cast the 28-year-old actress, Moffat said they need to "do better" at working towards getting a more varied cast.
He told Doctor Who magazine: "We decided that the new companion was going to be non-white, and that was an absolute decision, because we need to do better on that. We just have to.
"I don't mean that we've done terribly - our guest casts are among the most diverse on television - but I feel as though I could have done better overall."
Moffat - who began working on 'Doctor Who' in 1999 - is due to retire from the show at the end of 2017 and is set to hand over the reins to 'Broadchurch' director Chris Chibnall, but he hopes the new producer will encourage a more diverse cast when he takes over from him.
He said: "We've kind of got to tell a lie. We'll go back into history and there will be black people where, historically, there wouldn't have been, and we won't dwell on that."
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