There are many designs of flip book available, and Tim has quite a few in his collection. However this particular flip book contains an extra element - the basis of a magic trick.

The first page contains three pictures, one is a set of car keys, one is a watch, and the last is a pen.

One way of doing the trick is to offer someone the choice of the keys to your luxury car, a gold watch, or an executive pen. They are free to choose, but the only proviso is that if the item has already been taken, then they can't claim it.

Well, would you believe it! Whichever item you choose, the person holding the flip book flips the pages, and the exact item you had chosen turns out to be taken! There is only one flip book. Can you see how the trick works?