Catherine Tate with David TennantCatherine Tate and David TennantGuess who's going to be the new assistant 'bovvering' Doctor Who?

You guessed it, the new who in the zoo is Catherine Tate.

Catherine will be appearing in the fourth Doctor Who series as her previous character, Donna.

Donna was seen by fans in last year's Christmas special, The Runaway Bride.

At the press screening of the festive episode, when asked if she'd like to step into the shoes of Doctor Who's new assistant, Catherine commented: "I would love to, but no-one has asked."

Now they've asked and she's said yes.

The show's executive producer and head writer, Russell T Davies, said: "Catherine was an absolute star in The Runaway Bride and we are delighted that one of Britain's greatest talents has agreed to join us for the fourth series."

Catherine added: "I am delighted to be returning to Doctor Who. I had a blast last Christmas and look forward to travelling again through time and space with that nice man from Gallifrey."

Happy travels, Catherine!