Where tax is chargeable under section 65 of this Act on any occasion after a reduction and the rate at which it is charged is determined under section 69 by reference to the rate that was (or would have been) charged under section 64 on an occasion before that reduction (or before that and one or more other reductions), the rate charged on the later occasion shall be determined as if . . . F1F2the Table in Schedule 1 as substituted by that reduction (or by the most recent of those reductions) had been in force on the earlier occasion.