3BE+WA tenancy—
(a)which was entered into before 1st April 1990 or, where the dwelling-house had a rateable value on the 31st March 1990, on or after 1st April 1990 in pursuance of a contract made before that date, and
(b)under which the rent for the time being payable is less than two-thirds of the rateable value of the dwelling-house on 31st March 1990.