Where a United Kingdom ship or a ship registered in any other country is in a port in the United Kingdom and a person who is neither in Her Majesty’s service nor authorised by law to do so—
(a)goes on board the ship without the consent of the master or of any other persons authorised to give it; or
(b)remains on board the ship after being requested to leave by the master, a constable, an officer authorised by the Secretary of State or an officer of customs and excise,
he shall be liable on summary conviction to a fine not exceeding level 5 on the standard scale.