Section 39A of the Planning and Compulsory Purchase Act 2004 (c. 5) (“the Act”), as inserted by section 100 of the Levelling-up and Regeneration Act 2023 (c. 55), established a power for a plan-making authority to notify a prescribed public body in writing that the authority requires the body to assist the authority in relation to the preparation or revision of a relevant plan under section 39A(5) of the Act by the authority. Where this power is exercised, the prescribed public body must do everything that the plan-making authority reasonably requires of the body to assist the authority in relation to the preparation or revision of the relevant plan.