23.—(1) Any notice or other document required or authorised to be sent to the licensee under these Regulations shall be duly sent if it is sent by post in a registered letter or by recorded delivery to, or delivered to, or left for, the secretary or clerk of the licensee at its registered or principal office in the United Kingdom or at the address stated in the notice of appeal.
(2) A notice of appeal required to be served on the Secretary of State shall be duly served if it is sent by post in a registered letter or by recorded delivery to him at or left at 2-4 Cockspur Street, London SW1Y 5DH.
(3) If a notice of appeal is sent by registered post or recorded delivery, it shall be treated as if it had been received on the date on which it is received for despatch by the Post Office.
(4) In this regulation “the licensee” has the same meaning as in Part II of these Regulations or, where appropriate, Part III of these Regulations.