Input (grade 12): The race rotated between Silverstone, Aintree and Brands Hatch from 1955 to 1986, but relocated permanently to Silverstone in 1987.
Output (grade 6): The race rotated between Silverstone, Aintree and Brands Hatch from 1955 to 1986. In 1987 the rotation stopped and the race stayed at Silverstone.