"Sontarans are great," enthused the Doctor Who star in an exclusive chat with Doctor Who Magazine.
"I think that's partly because they come from a very specific world. That back story gives them a great context. Robert Holmes didn't just create a race, back in the 1970s: he created a world that they came from. Even if you never saw that planet, you understood why they did what they did."
Also in the latest issue: Georgia Moffett discusses what it's like being the Doctor's Daughter; Russell T Davies reveals all about Partners in Crime's top secret scene in Production Notes; a crisis in the Caribbean as Donna makes her comic strip début in Part One of The Widow's Curse; plus behind-the-scenes features on The Fires Of Pompeii and Planet Of The Ood.
Doctor Who Magazine issue 395 is out on Thursday 01 May 2008, priced at £3.99.