Freehold property acquired before 1 August 1999 is depreciated on a reducing balance basis at an annual rate of 1.33%. The assets' residual values and useful lives are reviewed and adjusted if appropriate at each reporting date. Assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. Any impairment charges arising are recognised in the income statement when the carrying amount of an asset is greater than the estimated recoverable amount, which is the higher of an asset's fair value less costs to sell and value in use, and are calculated with reference to future discounted cash flows that the asset is expected to generate when considered as part of a cash-generating unit. Prior impairments are reviewed for possible reversal at each reporting date. Gains and losses on disposals are determined by comparing the proceeds with the carrying amount and are recognised within operating expenses within the income statement