'There's not a lot of future in writing books' - Terry Deary
'I didn't expect Horrible Histories to be selling 20 years later' - Terry Deary

Talk us through the genesis of Horrible Histories

I was a children's author and a professional actor. I'd published about 50 novels and a Father Christmas joke book, which was a great success, so in 1992 they asked if I would write a history joke book. I'm not a historian so I got some researchers to find out things and I found the facts were more interesting than the jokes, so instead of a joke book with facts in, we ended up with a fact book with jokes in.

All school books [before] had been written by historians, experts and teachers and are deadly dull, so to have somebody who's actually a children's author write and re-present this material in an attractive, reader-friendly way was something rather revolutionary and so Horrible Histories were born. Then 1995 was the anniversary of the end of World War II and we did a book called Blitzed Brits and because it was fresh and new, that really took off and it went straight to the top of the children's bestsellers and it was suddenly a sensation. What I didn't expect was Horrible Histories to be selling 20 years later.

Do you count yourself a history buff?

Absolutely not. I have to read history books now to research my novels and new Horrible Histories but I'm not a historian and some of the things historians write, I find hard to swallow. These people are out to sell books and I'm starting to spot the distortions and the way they twist facts and make assumptions so I don't really like historians at all and if anybody called me one, I'd probably set fire to their house!

Do you have a favourite of the series?

Yes. They asked me to do a Horrible Histories of the English language. It wasn't a bestseller, but because I'm an author and I enjoy words, that was great fun to write. It was called Wicked Words.

What does the theatrical version offer that the books can't?

Firstly, with a book you've obviously got to be able to read whereas the theatrical version you don't have to. I took my twin grandchildren along to see Horrible Histories - Groovy Greeks on the stage and at four, they're not readers yet, but they were able to relate to the stories being told on the stage because they were being presented in an entertaining way. Secondly, you can bring the characters to life. I think the books are more historically accurate, whereas in the plays we play around with character and put words into people's mouths, which I can't do in the books.

What can we expect from Part Three?

It goes back to the Stone Age, which we've never done, and there are weird stories, all true, about keeping the heads of your relatives in your living room... We've also got a Viking song and a Magna Carta one because that's quite topical; we've got puritans banning Christmas, we've got a rap with King Charles II. We're doing a bake off because that's how the Great Fire of London started, so it's The Great Fire of London Does Bake Off. There's also Nelson trying to get compensation for losing his eye, a cholera outbreak for the Victorians, World War I and World War II.

You're making a cameo - can you tell us more?

I'm a professional actor but I've never appeared in the West End, so this will be my West End debut. I'm just doing the one performance on 27 July. It's a gala performance so I go down on the Sunday and rehearse it. My main part is as a Tudor executioner who's training up an apprentice. I also play a Viking and... I've forgotten the other two roles. I'll have to learn them.

Do you have anything in the pipeline after Barmy Britain ?

We're doing a series called Top 50 Disasters. For me, there's not a lot of future in writing books, it's getting harder and harder to make a living from so I'm planning a pirate's exhibition and I'm looking at a television series based on a fictional idea I've got. I'm also acting in a zombie movie which is released in September. I quite like doing films because I don't have to repeat it endlessly. When you do a stage play, you do the same part twice daily and it becomes a bit of a chore but a movie or television show is always a one off. I've got a lot of fiction still to write and I've got a novel called Silver Hand which I'm researching, about how the First World War really ended.

Horrible Histories - Barmy Britain: Part Three is at the Garrick Theatre from 25 July 2015