Paragraph 8 I1

the retail prices index for August 2001 or, following a revision in tolls in accordance with this Schedule or section 13 of the 1976 Act as amended by this Order, the month which is 2 months before the month in which falls the date upon which the last revision in tolls took effect; and

the retail prices index for the month 2 months prior to the month in which the change in the level of tolls is to have effect, or if no such index is available, the most recent month in respect of which the retail prices index has been published.