The news that Peter Capaldi is stepping down as Doctor Who has provoked the usual debate about his replacement being a woman or black. In recent times the series has established that either is possible but it should not be done for the sake of political correctness. Hopefully the production team will pick the best person, regardless of gender or colour.

Doctor Who has embraced diversity for 53 years. The first episode in 1963 was produced by a woman and directed by a Anglo-Asian. In 1965 it portrayed Arabic culture with integrity and later stories tackled themes of discrimination and intolerance with varying degrees of subtlety. The Doctor has had strong female companions, notably Sara (1965-6) and Leela (1977-78) and intelligent ones Zoe (1968-9), Liz (1970) and Romana (1978-81). Another Captain Jack Harkness (2005-10) was openly bisexual. Since the series returned in 2005 it has successfully cast many black actors in roles that might previously have been denied them.

Acting is one of the few professions where it is not always possible to avoid discrimination. Casting directors will not consider casting a white man to play Martin Luther King or a black woman to play Winston Churchill. They look at the character and then seek an actor of the right gender, age, height, physical appearance and race. No such restrictions apply to writers. They can be from any background so why are so many of them white males?

Television and film starts with the script. We need more black writers working on top shows. Creating characters that are written as black rather than race neutral. If the industry can ensure equality in its writers, then that will create the diverse range of roles required by the actors.