The Internal Drainage Boards (Finance) Regulations 1990

6.  In determining for the purposes of paragraph 2 above the level of rents current on 1st April 1988 for comparable lettings, account may be taken of any available evidence with respect to the rents which are, or were, payable in respect of tenancies of comparable agricultural holdings on terms (other than terms fixing the rent payable) similar to those of the tenancy under consideration, but the following shall be disregarded–

(a) any element of the rents in question which is due to appreciable scarcity of comparable holdings available for letting on such terms compared with the number of persons seeking to become tenants of such holdings on such terms;

(b) any element of those rents which is due to the fact that the tenant of, or a person tendering for, any comparable holding is in occupation of other land in the vicinity of that holding that may conveniently be occupied together with that holding; and

(c) any effect on those rents which is due to any allowances or reductions made in consideration of the charging of premiums.