(1)No oil tanker shall proceed, or attempt to proceed, to sea unless—
(a)it is a certificated oil tanker (within the meaning of Schedule 3 to this Act), or
(b)it is not registered in the United Kingdom, and—
(i)if it were a United Kingdom oil tanker, it would qualify for the issue of a tanker exemption certificate, or
(ii)its gross tonnage is less than 150 tons, or
(c)the Secretary of State has issued it with leave to sail.
(2)Where an application is made for leave to sail to be issued to an oil tanker, then—
(a)if the tanker is registered in the United Kingdom, the Secretary of State may issue it with leave to sail where he considers it appropriate to do so;
(b)if the tanker is not registered in the United Kingdom, the Secretary of State—
(i)shall issue it with leave to sail if he is satisfied that it would qualify for the issue of a tanker construction certificate if it were a United Kingdom oil tanker; and
(ii)may, if he is not so satisfied, issue it with leave to sail where he considers it appropriate to do so.
(3)Leave to sail issued under paragraph (a) or (b)(ii) of subsection (2) above may be issued subject to conditions imposed with a view to preventing or limiting the danger of oil pollution, including—
(a)conditions as to the cargo with which the tanker may sail;
(b)a condition that the tanker sails only to a specified port in the United Kingdom or elsewhere.
(4)Subject to subsection (5) below, if—
(a)an oil tanker proceeds, or attempts to proceed, to sea in contravention of subsection (1) above; or
(b)leave to sail having been issued to an oil tanker under this section subject to conditions, it proceeds to sea but the conditions are not complied with,
the owner and master of the tanker shall each be liable on summary conviction to a fine of not more than £10,000, or on conviction on indictment to a fine.
(5)In proceedings under subsection (4) above, it shall be a defence to prove that in order—
(a)to ensure the safety of the oil tanker, or
(b)to reduce the risk of damage to any other vessel or property,
it was necessary for the tanker to proceed to sea in contravention of subsection (1) above or, as the case may be, without complying with the conditions mentioned in paragraph (b) of subsection (4). In this section " damage " does not include damage caused by contamination resulting from the escape or discharge of oil from a tanker.