The Doctor had to face a very different Clara Oswald in the Saturday’s episode, as Jenna Coleman played Bonnie, an alien Zygon duplicate of herself.
“I loved evil Clara, I thought she was great,” said Capaldi in a BBC video about the episode. “I thought Jenna was a great evil creature.
“I thought she did it brilliantly, I think she should have her own series”
But playing two characters also had its challenges, said Coleman. “You’re playing Bonnie while also trying to remember the performance you’ve given as Clara in your head so it’s quite lonely. I was glad when Peter came to set and I had someone to look at and act against again.”