124 Expenditure qualifying for allowances.U.K.
(1)No expenditure shall be taken into account for the purposes of [writing-down allowances or] section 122, unless it is incurred for the purposes of husbandry on the agricultural land in question, and—
(a)where the expenditure is on a farmhouse, one-third only of the expenditure shall be taken into account, or, if the accommodation and amenities of the farmhouse are out of due relation to the nature and extent of the farm, such proportion thereof not greater than one-third as may be just,
(b)where expenditure is incurred on any asset other than a farmhouse, being an asset which is to serve partly the purposes of husbandry and partly other purposes, such apportionment of the expenditure shall be made for the purposes of [writing-down allowances or, as the case may be, section 122] as may be just.
(2)In any case where—
(a)capital expenditure is incurred on the construction of any building, fence or other works, but
(b)when the building, fence or other works comes to be used it is not used for the purposes of husbandry,
the expenditure shall be left out of account for the purposes of [writing-down allowances] and, accordingly, any writing-down allowance made in respect of the expenditure under section 123 shall be withdrawn and all such assessments and adjustments of assessments shall be made as may be necessary to give effect to that withdrawal.
(3)Where an allowance or charge is or has been made under section 24 by reference to an amount of qualifying expenditure which took account of a particular amount of capital expenditure, that capital expenditure shall be left out of account for the purposes of this Part.
This subsection shall not have effect in relation to any chargeable period ... ending after 26th July 1989.