If, immediately before the revocation of regulation 68CB of the Defence (General) Regulations 1939 accommodation was registered for the purposes of that regulation and was let in accordance with the terms and conditions so registered, any contract for the letting of the accommodation shall be treated, for the purposes of this Act, as not being a restricted contract, so long as any letting continues under which the accommodation was let in accordance with the terms and conditions on which it was let immediately before the revocation.