How to make Big Ben's clock strike 13

Help

How is it possible to make Big Ben strike 13 o'clock? There aren't that many numbers on the clockface.

Greg Foot plays with sound and time to make Big Ben chime 13 times at midnight.

Secrets of the Universe is on BBC Three at 8pm on Thursday 4 November or watch online afterwards via iPlayer at the above link.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.