15(1)If—
(a)under the contract of employment under which a shop worker who satisfies the conditions in paragraph 2(2)(a) and (b) above was employed on the day before the commencement date, the shop worker was or might have been required to work on Sunday before that date,
(b)the shop worker has done shop work on Sunday in that employment (whether or not before the commencement date) but has, on or after the commencement date, ceased to do so, and
(c)it is not apparent from the contract what part of the remuneration payable, or of any other benefit accruing, to the shop worker was intended to be attributable to shop work on Sunday,
then, so long as the shop worker remains a protected shop worker, that contract shall be regarded as enabling the employer to reduce the amount of remuneration paid, or the extent of the other benefit provided, to the shop worker in respect of any period by the proportion which the hours of shop work which (apart from this Schedule) the shop worker could have been required to do on Sunday in the period (in this paragraph referred to as “the contractual Sunday hours”) bears to the aggregate of those hours and the hours of work actually done by the shop worker in the period.
(2)Where, under the contract of employment, the hours of work actually done on weekdays in any period would be taken into account in determining the contractual Sunday hours, they shall be taken into account in determining the contractual Sunday hours for the purposes of sub-paragraph (1) above.