“I’d already started work on a story about one of those idealised Victorian mill communities and tailored it to suit Diana and Rachael. I wanted to do a properly northern Who – it’s underexplored in the show – and Diana used her native Doncaster accent for the first time!I wanted the adventure to feel very distinctive and it really does. A lurid, Victorian penny-dreadful with Vastra, Jenny and Strax and ’orrible murder. It’s very me!”