The Agriculture (Calculation of Value for Compensation) Regulations 1978

(2) If the value of any work, calculated in accordance with sub-paragraph (1) above, exceeds the actual value to an incoming tenant, in any case where—

(a) plans on a suitable scale, made at the time when the work was done, and showing the position of all moles, mains and outfalls, are not made available to the landlord; or

(b) moles were not drawn at a proper depth, having regard to the nature of the soil and subsoil; or

(c) any ditches into which the outfalls discharge have not been maintained clean, free from obstruction and at a proper depth since the work was done; or

(d) deep cultivation or other work interfering with the efficient functioning of the drains has been done on the land since the drainage work was completed; or

(e) the land is not of consistently suitable slope or soil texture for mole drainage to be effective; or

(f) the drainage scheme was not a proper one, having regard to all the conditions, or was not efficiently carried out; or

(g) for any other reason, the drainage system does not function efficiently,

the value so calculated shall be reduced so as not to exceed such actual value.