Did you try replacing batteries?
Check the gear connected to the engine located in the bottom Graham. You will need to remove a small plastic cover.
I have 2 of them and I had problems with both. Fortunately fix them were not a big deal.
Actually it has a very, very fragile mechanism
ahhhh, Qrusader, don't forget to remove the cardboard from the top and the plastic box containg the fist BEFORE of turn it on!