| All fixed assets are initially recorded at cost. Property, plant and equipment is used in the company's principal activity for the production and supply of goods or for administrative purposes. Land and buildings are stated in the balance sheet at their revalued amount, being fair value at the date of revaluation less any subsequent accumulated depreciation and accumulated impairment losses. Revaluation gains are recognised in other comprehensive income and accumulated in the revaluation reserve. Revaluation decreases, including impairment losses on revalued land and buildings, are recognised in other comprehensive income to the extent of any previous revaluation surplus for that asset, with any excess recognised in profit or loss. All other property, plant and equipment is stated under the historic cost model, at cost less amounts in respect of depreciation and less any accumulated impairment losses. No depreciation is provided on the leasehold property, which is held on a very long lease. The directors consider that its remaining useful life is so long, and its residual value so close to its carrying amount, that any depreciation charge would be immaterial. The property is reviewed for impairment at each reporting date. Depreciation is calculated so as to write off the cost or valuation of an asset, less its estimated residual value (which is the expected amount that would currently be obtained from disposal of an asset, after deducting the estimated costs of disposal, if the asset were already of the age and in the condition expected at the end of its useful life), over the useful economic life of the respective asset as follows: |