Doomsday - Whose Finest Treasure?

The Doomsday Book is now available online at the National Archives website.

When I did history at secondary school I was told that the Doomsday book was commissioned by William the Conquerer about 20 years after he became king of England some 600 years before "Britain" existed which is a bit confusing when the National Archives website says that it's Britain's Finest Treasure.

The Doomsday Book is English, not British.