10 at the most
If they didn't win Britain would be talking German (probably) yes they did win
British civilian deaths during the second world war are estimated at between 60 000 and 70 000.
RAF=498 and Luftwaffe=690
250 RAF pilots died in the Battle of Britain
French Surrender and the Final Solution in 1940
Prince William Co-Pilots Helicopter Rescue
Persuading the Americans to Join WWII
Prince's Falklands Duty Tour