10.—(1) Where any lease or agreement (however worded) entered into before the commencement date has the effect of requiring the occupier of a shop to keep the shop open for the serving of retail customers—
(a)during normal business hours; or
(b)during hours to be determined otherwise than by or with the consent of the occupier,
that lease or agreement shall not be regarded as requiring, or as enabling any person to require, the occupier to open the shop on Sunday for the serving of retail customers.
(2) Paragraph (1) shall not affect any lease or agreement—
(a)to the extent that it relates specifically to Sunday and would (apart from this Article) have the effect of requiring Sunday trading of a kind which before the commencement date would have been lawful by virtue of any provision of Part I of the [1946 c. 7 (N.I.).] Shops Act (Northern Ireland) 1946; or
(b)to the extent that it is varied by agreement after the commencement date.