Article 4
Where an offence is alleged to have been committed on board any ship belonging to the Spanish State by the master or a member of the crew, proceedings for the offence instituted otherwise than at the request or with the consent of a consular officer of the Spanish State shall not be entertained by any court in the United Kingdom, unless—
the offence is alleged to have been committed—
by or against a person who is a citizen of the United Kingdom and Colonies, a citizen of Southern Rhodesia, a British subject by virtue of sections 2, 13 and 16 of the British Nationality Act 1948 or the British Nationality Act 1965, or a British protected person within the meaning of the said Act of 1948; or
against a person other than the master or a member of the crew; or
the offence is one involving the tranquillity or safety of a part, or the law relating to safety of life at sea, public health, oil pollution, wireless telegraphy, immigration or customs; or
the offence is one punishable (on a first conviction) with imprisonment for a term that may extend to five years or with a more severe sentence.