(1) Where-

(a) there exist a number of debts, and

(b) the person liable therefor (in this section referred to as the debtor) makes any payment, whether on account or generally, to the person to whom he is liable (in this section referred to as the creditor), and

(c) neither the debtor nor the creditor appropriates the sum paid to any particular debt or debts; the following provisions shall have effect:-

(i) if some of or all the debts are not statute-barred, the payment shall, for the purposes of this Part of this Decree, unless the circumstances in which it was made indicate otherwise, be deemed to be appropriated pari passu in respect of each of the debts which are not statute-barred;

(ii) if all the debts are statute-barred, then the payment shall for the purposes of this Part of this Decree, unless the circumstances in which it was made indicate otherwise, be deemed to be appropriated pari passu in respect of all of the debts; so however that no such appropriation shall operate to make the payment a payment for the purposes of sections 19 and 20 of this Decree unless the circumstances in which the debtor made the payment indicate otherwise.

(2) Nothing in subsection (1) of this section shall, where the debtor does not appropriate, operate to prevent the creditor from appropriating a payment on account or generally to a particular debt or to particular debts or to all the debts (whether statute-barred debts or not), but such appropriation shall not by reason only of its being made by the creditor operate to make the payment a payment for the purposes of sections 19 and 20 of this Decree in respect of any of such debts which are statute-barred, unless the circumstances in which the payment was made by the debtor so indicate.