What are the statutory requirements concerning proceeding on a domestic UK voyage or excursion without the appropriate certificate?

A passenger ship of Class II(A), III, IV, V, VI or VI(A) may not proceed on a voyage or excursion unless it has been surveyed and there is in force a Passenger Certificate appropriate to the ship's class and applicable to that voyage or excursion. Where a certificate is issued subject to conditions, the ship may not proceed on a voyage or excursion unless all the conditions are complied with.