Missing Square 

Using gridded paper, you can mark out the following design and cut out the various bits. However, if you rearrange the pieces as below, you are left with a missing square - how?

According to the 'Missing square puzzle' Wikipedia Page the puzzle was created by Paul Curry, an amateur magician.

Don't believe it? Print this page out, cut out the pieces and try it! If you can't work out how this magic works, then have a quick look at the answer.