The most striking feature of Wembley Stadium is the is 133 metre tall steel arch that sits above the north stand. And it's not just any arch — it's an inverted catenary. Paul Shepherd, engineer and builder of sports stadiums, explains what makes the catenary so special and why it, as well as eggs, are so important in architecture.

You can find out more about the catenary in this short article. To find out more about Paul Shepherd's work building football stadiums listen to this podcast.