Tangible fixed assets are measured at cost less accumulated depreciation and any accumulated impairment losses. Depreciation is provided at rates calculated to write off the cost of the fixed assets, less their estimated residual value, over their expected useful lives on the following bases:

Assets obtained under finance leases are capitalised as tangible fixed assets. Assets acquired under finance leases are depreciated over the shorter of the lease term and their useful lives. Assets acquired under hire purchase contracts are depreciated over their useful lives. Finance leases are those where substantially all of the benefits and risks of ownership are assumed by the company. Obligations under such agreements are included in the creditors net of the finance charge allocated to future periods. The finance element of the rental payment is charged to the profit and loss account so as to produce a constant periodic rate of charge on the net obligation outstanding in each period.

Rentals applicable to operating leases where substantially all of the benefits and risks of ownership remain with the lessor are charged to profit and loss account as incurred.

Stocks and work in progress are valued at the lower of cost and net realisable value after making due allowance for obsolete and slow-moving stocks. Cost includes all direct costs and an appropriate proportion of fixed and variable overheads. Work-in-progress is reflected in the accounts on a contract by contract basis by recording turnover and related costs as contract activity progresses.