Meet the young mathematician who helped design the Spitfire, the iconic aircraft that took part in the Battle of Britain, which started 80 years ago today.
Hazel Hill helped her father do the calculations that meant Spitfire's could be built with eight guns instead of four. Many believe this made a big difference to the outcome of the Battle of Britain.
'The Schoolgirl who Helped Win a War' will be broadcast on the BBC News Channel at 13.30, 17.30 and 20.30 on Saturday and 10.30 and 16.30 on Sunday. It will also be available on BBC iPlayer.
