Please answer the following question: Given the following passage  "In 1951, the Conservative Party returned to power in Britain, under the leadership of Winston Churchill. Churchill and the Conservatives believed that Britain's position as a world power relied on the continued existence of the empire, with the base at the Suez Canal allowing Britain to maintain its pre-eminent position in the Middle East in spite of the loss of India. However, Churchill could not ignore Gamal Abdul Nasser's new revolutionary government of Egypt that had taken power in 1952, and the following year it was agreed that British troops would withdraw from the Suez Canal zone and that Sudan would be granted self-determination by 1955, with independence to follow. Sudan was granted independence on 1 January 1956.",  answer the following question. Note that the answer is present within the text.  Question: What did Churchill believe was necessary?
A:
base at the Suez Canal