21.—(1) The Secretary of State may, to such extent and subject to such restrictions and conditions as he may think proper, delegate or authorise the delegation of any of his powers under this Order to any person, or class or description of persons, approved by him, and references in this Order to the Secretary of State shall be construed accordingly.
(2) Any licences granted under this Order shall be in writing and may be either general or special, may be subject to or without conditions, may be limited so as to expire on a specified date unless renewed and may be varied or revoked by the authority that granted them.