After swimming the length of the Thames for Sport Relief David Walliams now turns his attention to the stage adaptation of his second children's novel Mr Stink. He talked to James Rampton about the first ever scratch and sniff musical.

First things first, you've just swam 140 miles of the Thames in just eight days in aid of Sport Relief, despite the cold, windy and rainy conditions and a serious stomach upset. What are your thoughts on the swim now?

It was a lot colder than I thought, the weather wasn't good and I got ill so there were a lot of things against me but I just knew that if I kept putting one arm in front of the other I would eventually get there.

I was overwhelmed by the generosity of the British public. The fact they came out and saw me and waved and cheered really made it a lot easier.

What was your initial reaction when you were approached about the idea of Mr Stink live on stage?

I was very flattered. It's really exciting to think that a book you've written will have another life. What could be better?

Why do you think this story translates so well to the stage?

Like a lot of children's books, it contains very vivid characters. They are ripe for the theatre because they're so bold. They leap off the page.

They're almost like cartoon characters who really suit being on stage - unlike more subtle characters who might get lost in the theatre.

When Matt Lucas and I worked in the theatre on Little Britain Live, the characters almost worked better there than they did on TV because they were so over the top. In the same way, this story feels instantly dramatic.

Are you looking forward to seeing how children react to Mr Stink live on stage?

Yes. When I started writing children's books, I was aware that loads of kids loved Little Britain, but a lot of it was quite rude for them. So it's great to do something specifically for children where parents don't have to worry that it might be too rude or be embarrassed to watch with their children.

It's lovely to have a show that the whole family can enjoy together.

Can you please tell us about the fact that it will be a scratch and sniff production?

It is actually the world's first ever scratch and sniff theatre production. That was my idea. I felt it would be terrific fun to create this interactive element.

If I was a kid, I'd love to go to this show, and be told to scratch and sniff No2 and get this disgusting smell from it. Children are restless. They don't want to sit in silence for the entire show. They want to be involved, to be frightened and to have a laugh.

They want to feel part of the show. Even if you've read the book, scratch and sniff offers something a bit different. It's a great way of getting children involved. They can rest assured, all the smells will be horrible!

Why has this work - known as the smelliest book of all time - struck such a chord with children?

I put a child at the centre of the story, and I try to reflect what it is really like to be that age. A lot of children's books are about wish fulfilment - children as superheroes and spies.

But I show children as powerless - as you are as a child. When you're very young, you don't get to choose many things - your house, say, or your school. You're in that situation, and there's not a lot you can do about it.

In this story, the central character Chloe transforms her family through her friendship with a tramp. In that way, the most powerless person in her family becomes the most powerful.

David Walliams' Mr Stink Live comes to Tunbridge Wells' Assembly Hall Theatre on Friday, October 7 and Saturday, October 8.