Any contract of employment under which a shop worker or betting worker who satisfies section 36(2)(a) was employed on the day before the relevant commencement date is unenforceable to the extent that it—
Subject to subsection (3), any agreement entered into after the relevant commencement date between a protected shop worker, or a protected betting worker, and his employer is unenforceable to the extent that it—
Where, after giving an opting-in notice, a protected shop worker or a protected betting worker expressly agrees with his employer to do shop work or betting work on Sunday or on a particular Sunday (and so ceases to be protected), his contract of employment shall be taken to be varied to the extent necessary to give effect to the terms of the agreement.
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For the purposes of section 36(2)(b), the appropriate date—