Super Nanny

"Miss Foster is, essentially, a nanny, a guardian, to some rather unusual children," explained Sarah in an interview for the latest issue of Doctor Who Magazine.

"I see her as a slightly warped Mary Poppins. She's quite austere. She's a strong woman. When I first read the script, I thought, oh, well, of course she's a baddie... but the more I read it, I thought, 'No, she's doing what she's doing for legitimate reasons.'"

"You can't blame her at all. Hers is perfectly reasonable behaviour..."

Other things to look out for in the new issue include: executive producers Russell T Davies, Julie Gardner and Phil Collinson answering the most probing of questions as DWM's readers become the interviewers; previews of Partners in Crime, The Fires of Pompeii, Planet of the Ood and The Sontraran Stratagem/The Poison Sky; and an interview with award-winning writer Steven Moffat - who breaks his silence about his forthcoming two-parter, Silence in the Library/River's Run.

Doctor Who Magazine is out on 03 April 2008, price £3.99.