From the Annual accounts:RevaluationsFollowing initial...

From the Annual accounts:

Revaluations
Following initial recognition at cost, land and buildings (other than investment property) are carried at a revalued amount which is the fair value at the date of the revaluation less any subsequent accumulated depreciation on buildings and subsequent accumulated impairment losses.
Fair value is determined by reference to market-based evidence, which is the amount for which the assets could be exchanged between a knowledgeable willing buyer and a knowledgeable willing seller in an arm’s length transaction as at the valuation date.
Any revaluation increment related to property, plant and equipment (other than investment property), is credited to the asset revaluation reserve included in the equity section of the balance sheet unless it reverses a revaluation decrease of the same asset previously recognised in the income statement, in which case the increment is recognised in the income statement.
Any revaluation decrement is recognised in the income statement unless it directly offsets a previous increment of the same asset in the asset revaluation reserve, in which case it is charged directly to the asset revaluation reserve to the extent of the previous increment existing in relation to that asset.

An annual transfer from the asset revaluation reserve to retained earnings is made for the difference between depreciation based on the revalued carrying amounts of the assets and depreciation based on the assets’ original costs.
In addition, any accumulated depreciation as at revaluation date is eliminated against the gross carrying amount of the asset and the net amount is restated to the revalued amount
of the asset.
Upon disposal, any revaluation reserve relating to the particular asset being sold is transferred to retained earnings.
Independent valuations are performed with sufficient regularity to ensure that the carrying amount does not differ materially from the asset's fair value at the balance sheet date.
An item of property, plant and equipment is derecognised upon disposal or when no future economic benefits are expected to arise from the continued use of the asset.
Any gain or loss arising on de-recognition of the asset (calculated as the difference between the net disposal proceeds and the carrying amount of the item) is included in the income statement in the period the item is derecognised.