Which king/queen of Britain was the most successful in fulfilling his/her duties and why?

William the Conqueror, I think. Not only captured the country, but consolidated his power and brought order.

More successful kings & queens:
- Alfred the Great - defeated danes
- Cnut the Great - created North Empire
- Edward 1 Longshanks - captured Wales and Scotland
- Henry 5 - captured France
- Elizabeth 1 - The Great England
- George 4 (as prince-regent) - defeated Napoleon
- Victoria - British empire
- George 6 - victory in 2 World war
- Elizabeth 2