http://www.legislation.gov.uk/ukpga/2003/20/section/84/enactedRailways and Transport Safety Act 2003PoliceRail safetyTrade unionsKing's Printer of Acts of Parliament2021-08-04 Part 4 84 1 A marine official may detain a ship if he reasonably suspects that a person who is or may be on board the ship— a is committing an offence under section 78, 79 or 80, or b has committed an offence under section 78, 79 or 80. 2 The power of detention under subsection (1)— a is conditional upon the marine official making a request, either before the detention or as soon as possible after its commencement, for a constable in uniform to attend, and b lapses when a constable in uniform has decided whether or not to exercise a power by virtue of section 83 and has informed the marine official of his decision. 3 In this section “marine official” means— a a harbour master, or an assistant of a harbour master, appointed by a harbour authority, b a person listed in section 284(1)(a) to (d) of the Merchant Shipping Act 1995 (c. 21)(detention of ship), and c a person falling within a class designated by order of the Secretary of State. 4 In construing section 284(1)(b) of the Merchant Shipping Act 1995 (detention by person authorised by Secretary of State) for the purpose of subsection (3)(b) above, the reference to authorisation to exercise powers under that section shall be taken as a reference— a to general authorisation to exercise powers under that section, and b to general or particular authorisation to exercise powers under this section.