"By that time taxes had become the prime source of revenue for the United Kingdom and Parliament administered the country, so an agreement was reached that the Crown Lands would be managed on behalf of the Government and the surplus revenue would go to the Treasury. In return the King would receive a fixed annual payment - today known as the Civil List. This agreement has, at the beginning of each reign, been repeated by every succeeding Sovereign.

In 1955 a Government Committee under the Chairmanship of Sir Malcolm Trustram Eve recommended that to avoid confusion between Government property and Crown land, the latter should be renamed The Crown Estate and should be managed by an independent board. These recommendations were implemented by the Crown Estate Acts of 1956 and 1961."

http://www.thecrownestate.co.uk/about_us/our_history.htm