What is the Mobile Phone Emergency Number?

Yolanda and I did a St John's First Aid course last weekend and one thing that surprised me was that I did not know the emergency number to dial from a mobile phone - it is not 999! If you dial the right number, apparently your phone will often show stronger signal strength than usual for that area when you dial that number.

Am I the only person who didn't know it?

OK yes, first person to guess gets it - well done Paul. It is 112