The world's most dangerous sandwich - Matt Brown and Compton Valance visit Mostly Books

'Compton Valance: The Most Powerful Boy in the Universe' is a funny, time-travel adventure based on a time machine disguised as a cheese and pickled egg sandwich.

It is Heart FM DJ Matt Brown's debut book. To celebrate, there will be sandwich ingredients hidden around Abingdon town centre shops throughout half-term. If you find them all, when put together, they may, or many not, give you the power to travel in time.

Gather together the secret ingredients and you may discover the key to time travel. You may, like Compton Valance, become the most powerful boy (or girl) in the universe. But beware. You wouldn't want to be guilty of putting the fabric of time at risk, or causing the custard cream-related extinction of the dinosaurs - would you? You wouldn't use your powers for anything other than good?

However, you may want to win a first prize of a terrific goody-bag of £40 worth of Usborne books.

And there will be tons of prizes of samples of Matt's book so that everyone can discover the hilarious Compton Valance for themselves - and a very loud whistle.

Start your sandwich trail at Mostly Books.

Just don't use any new amazing powers for evil. OK.

Update: Matt will be visiting several bookshops in Oxfordshire on Friday May 30 - and he'll be at Mostly Books at 2pm. Come on down, meet Matt, and blow those whistles...