Increase in certain lump sums
4. In respect of any lump sum or installment of a lump sum which became payable before 6th April 1998 but after 6th April 1997 there may be paid an increase of 3.6 per cent of the amount of the lump sum or instalment (as increased by the amount of any increase under section 1 of the Act of 1971 or under the existing Orders) multiplied by
where—
a
A is the number of complete months in the period between the beginning date for the lump sum (or, if later, 7th April 1997) and the date on which it became payable; and
b
B is 12.