[15U.K.Whether an increase in rent is to be regarded for the purposes of paragraph 14 as abnormal is determined as follows:—
[Step One
Find the start date. Where the provisions of paragraph 14 have not previously applied to an increase in the rent payable under the lease, the start date is—
(a)if paragraph (b) or (c) does not apply, the beginning of the term of the lease;
(b)if the amount of rent payable under the lease is determined under paragraph 7 (variable or uncertain rent), the beginning of the period by reference to which the rent assumed to be payable after the fifth year of the term of the lease is determined in accordance with paragraph 7(3);
(c)if there has been a variation in the lease falling within paragraph 13 (increase of rent treated as grant of new lease: variation of lease in first five years), the date of the variation (or, if there has been more than one such variation, the date of the most recent one).
Where the provisions of paragraph 14 have previously applied to an increase in the rent payable under the lease, the start date is the date of the last increase in relation to which the provisions of that paragraph applied.
Step Two
Find the number of whole years in the period between the start date and the date on which the new rent first becomes payable.
Step Three
The rent increase is regarded as abnormal if the excess rent (see paragraph 14(3)) is greater than:
where—
R is the rent previously taxed (see paragraph 14(4) or (4A)), and
Y is the number of whole years found under Step Two.]]