4.17.—(1) A creditor may state the amount of his claim in a currency other than sterling where -
(a)his claim is constituted by decree or other order made by a court ordering the company to pay to the creditor a sum expressed in a currency other than sterling, or
(b)where it is not so constituted, his claim arises from a contract or bill of exchange in terms of which payment is or may be required to be made by the company to the creditor in a currency other than sterling.
(2) Where a claim is stated in currency other than sterling for the purpose of the preceding paragraph, it shall be converted into sterling at the rate of exchange for that other currency at the mean of the buying and selling spot rates prevailing in the London market at the close of business on the date of commencement of winding up.