If at any time during the original maximum toll period it appears to the Secretary of State that the aggregate of relevant receipts and assumed interest receipts before the end of that period is likely to fall short of the aggregate of the amounts required during that period for the purposes so mentioned, he may by order direct that that period shall be extended by five years.

The power to make an order under this paragraph is exercisable on one occasion only.

No order shall be made under this paragraph unless a draft of the order has been laid before, and approved by a resolution of, the Commons House of Parliament.

References in this Part and in Part III of this Schedule to the relevant period are references to the original maximum toll period or, if that period has been extended under this paragraph, to that period as so extended.