The acquiring authority may agree in writing with the owner of any interest which is to vest in the authority under section 8 that the interest is to vest on a date before the vesting date.
The agreed date may not be before the day after the last day on which a person may bring proceedings for questioning the compulsory purchase order.
If an agreement under subsection (1) is in force—
section 7 (other than section 7(1)(c)) and section 8 operate in relation to the interest as if the vesting date were the agreed date;
an owner of an interest who is a party to the agreement may not serve a counter-notice under paragraph 2 of Schedule A1 (counter-notice requiring purchase of additional land).
But if the interest subject to the agreement does not entitle the owner to possession of the land concerned, subsection (3)(a) does not advance the date on which the right to enter on and take possession of the land arises under section 8.