20Duty to produce Convention certificate.
The master of every Safety Convention ship not registered in the United Kingdom, being a passenger steamer or being a ship of sixteen hundred tons gross tonnage or upwards, shall produce a valid Safety Convention certificate to the officer of customs, from whom a clearance for the ship is demanded in respect of an international voyage from a port in the United Kingdom after the expiration of twelve months from the commencement of this Part of this Act, and a clearance shall not be granted, and the ship may be detained, until such a certificate is so produced.