a ship’s tonnage shall be its net or register tonnage (as the case may be) entered in its certificate of tonnage issued by or on behalf of the administration of the State of Registry; or in the case of an unregistered vessel the tonnage reckoned in accordance with the Thames Measurement adopted by Lloyd’s Register;

a year shall be reckoned from 1st April;

in calculating any payment of light dues where the vessel’s tonnage is not a multiple of 10 tons, any excess not exceeding 5 tons shall be rounded down and any excess over 5 tons shall be rounded up to the nearest such multiple;

“home-trade”, in relation to any ship, means employed in trading or going within the following limits, that is to say the United Kingdom, the Channel Islands, the Isle of Man and the Republic of Ireland and the Continent of Europe between the north bank of the River Eider and Brest inclusive; and “home-trade limits” shall be construed accordingly;

“foreign-going”, in relation to any ship, means employed in trading or going between some place or places in the United Kingdom or the Republic of Ireland and some place or places situate beyond the following limits, that is to say the coasts of the United Kingdom, the Channel Islands, the Isle of Man and the Republic of Ireland and the Continent of Europe between the north bank of the River Eider and Brest inclusive;

“length” in relation to a fishing vessel means the registered length shown in the vessel’s certificate of registry and in relation to such a vessel having no registered length, means the length which would be the registered length if the vessel was registered under Part II of the Merchant Shipping Act 19886, provided that in calculating any payment of light dues where a fishing vessel’s length is not a multiple of one metre, any excess not exceeding half a metre shall be rounded down and any excess over half a metre shall be rounded up to the nearest such multiple;

“fishing vessel” means any fishing vessel registered under Part II of the Merchant Shipping Act 1988 or registered as a fishing vessel under the law of some other country;

“Ro/Ro ferry” means a ship–

provided with cargo or road or rail vehicle spaces extending to either a substantial length or the entire length of the ship in which vehicles or cargo can be loaded or unloaded normally in a horizontal direction;

which operates on regular advertised services available to accompanied motor vehicles or unaccompanied trailers on payment of an advertised fare or similar tariff charge; and

engaged on voyages which begin or end in the United Kingdom where neither the distance between the last outward port of call in the United Kingdom and the final port of destination nor the return voyage exceeds 700 nautical miles. The final port of destination is the last port of call in the scheduled voyage at which the ship commences its return voyage to the United Kingdom.