This is a little video that I have captured. Click on the image first to cause the movie to download and play once. Use the tiny "forward" arrow of the control to see it again, if you like. The left and right arrows on the right of the controls take you backwards and forwards one frame at at time. You can also drag the slider control back and forth with your mouse.

Technical note: Newer versions of Internet Explorer do not support the Quicktime plug-in any more. I have set up the web page to automatically download the Active-X control you need if you are affected by this problem - if you are prompted to download the control, this means you won't be able to view the movie if you don't. Other browsers are not affected by this problem.