157.—(1) Where, as a result of any occurrence, the owner of a ship incurs liability under section 153 by reason of a discharge or escape or by reason of any relevant threat of contamination, then (subject to subsection (3) below)—
(a)he may limit that liability in accordance with the provisions of this Chapter, and
(b)if he does so, his liability (being the aggregate of his liabilities under section 153 resulting from the occurrence) shall not exceed the relevant amount.
(2) In subsection (1) above, “the relevant amount” means—
(a)in relation to a ship not exceeding 5,000 tons, three million special drawing rights;
(b)in relation to a ship exceeding 5,000 tons, three million special drawing rights together with an additional 420 special drawing rights for each ton of its tonnage in excess of 5,000 tons up to a maximum amount of 59.7 million special drawing rights;
but the Secretary of State may by order make such amendments of paragraphs (a) and (b) above as appear to him to be appropriate for the purpose of giving effect to the entry into force of any amendment of the limits of liability laid down in paragraph 1 of Article V of the Liability Convention.
(3) Subsection (1) above shall not apply in a case where it is proved that the discharge or escape, or (as the case may be) the relevant threat of contamination, resulted from anything done or omitted to be done by the owner either with intent to cause any such damage or cost as is mentioned in section 153 or recklessly and in the knowledge that any such damage or cost would probably result.
(4) For the purposes of this section a ship’s tonnage shall be its gross tonnage calculated in such a manner as may be prescribed by an order made by the Secretary of State.
(5) . . .