The writer of Doctor Who has revealed how he protested against the “colour blind” casting of a black actor as a Victorian soldier in the BBC show.

Mark Gatiss said he was uneasy about a “brilliant young black actor” being cast as one of the soldiers, because “there weren’t any black soldiers in Victoria’s army”.

He put the decision down to the BBC’s drive to become “more representational and make everything less homogeneously white”.

Gatiss described the “very difficult” email he sent to a colleague explaining his feelings on the matter. It was only after he discovered records showing that there was in fact a single black soldier in Victoria’s army, that he accepted the decision.