Yes. 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 think I had this baffling idea that if we just threw open each part to everybody, it would work out in the end. I put my faith, inexplicably, in the free market. I don’t know why, I of all people would do that! It doesn’t work. You can only cast for talent – you’ve got to cast the best person, every single time – but you’ve got to gauge where you’re looking for that talent. … 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. Young people watching have to know that they’ve a place in the future. That really matters. You have to care profoundly what children’s shows in particular say about where you’re going to be.
Steven Moffat on the casting of Pearl Mackie and Diversity in the BBC (Doctor Who Magazine #500)