5. Julian Bleach
Best known for playing Dalek creator Davros in 2008 and 2015 episodes of Doctor Who, Bleach previously appeared in Torchwood as a breath-stealing villain called The Ghostmaker. And, completing the set, Bleach also played a Sarah-Jane Adventures villain, appearing as The Nightmare Man in a story of the same name.
6. Yasmin Bannerman
We all remember Bannerman’s performance as tree-lady Jabe in 2005 episode The End of the World – but you might not realise that she also cropped up in Torchwood playing DI Kathy Swanson, who investigated the team for a string of murders.