Jennifer Saunders plays Miss Dandy, who runs the Twilight Towers old people's home. She says she loves playing villains.

Adaptations of David's books have always been massively popular and successful - how did you feel when you were asked to be a part of it?

I was thrilled because I took a part in The Boy In The Dress, and really enjoyed it. I think what's lovely about David's stuff is that it's quite grown-up; the themes are grown up. That's why they make such great kids' books. And the characters are such huge fun. And he always gets great cast - the cast are just astounding. Everyone's having such fun!

Miss Dandy might be a bit more of a sinister character than initially meets the eye - how does it feel to play the villain?

I have to say, I think she's pretty sinister from when she first meets the eye! I love playing villains. They're so much more interesting than nice people. The costumes have been brilliant - the costume and make up teams have really pulled out all the stops. They've allowed the imagination to run riot.

She's a pretty hideous human being underneath it all. She's the sort of person you'd hope would never be in charge of an old people's home. But great fun because of that - there are so many sides to her. It's great being a villain - it's so easy, it comes naturally!

How would you sum up Miss Dandy in a few sentences?

She's a self-serving psychopath with very few redeeming features. She's very two-faced! She's one thing to the relations of the old people; and another when left alone with them. I think the fact that her tool of choice is a cattle-prod says a lot about her mentality.

What has been your favourite moment during filming Grandpa's Great Escape?

There's been so many, actually - we've had an absolute ball. Working with Tom Courtenay and Michele Dotrice has been an absolute joy. Watching Michele is like watching a lesson in comedy. There are people in the cast that I have looked up to and admired for years. A lot of my favourite moments are watching other people - Sam Spiro, Samson Kayo, Ricky Champ...

One of the funniest moments was wearing a breast-plate to play Miss Dandy; it was quite funny putting those on because they were rather large. David [Walliams] actually thought they were mine! He was somewhat disappointed when I took them off and came out without them.

What's your favourite thing about television over the Christmas period?

The fact that it's on most of the time. The fact that I think a lot of TV companies save up their special little treats for Christmas, so you get lovely little programmes like this - a one-off, a special, the end of a series. It's a great big fun-fest and it's classic to go through the TV magazines and work out how you're going to watch everything. There's so much planning involved - and when are we going to eat?! There's a lot to fit in. And it's good that there's a lot of entertainment on late, too. There's always something on!