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:

A lease is classified as a finance lease if it transfers substantially all the risks and rewards incidental to ownership. All other leases are classified as operating leases. The rights of use and obligations under finance leases are initially recognised as assets and liabilities at amounts equal to the fair value of the leased assets or, if lower, the present value of the minimum lease payments. Minimum lease payments are apportioned between the finance charge and the reduction in the outstanding liability using the effective interest rate method. The finance charge is allocated to each period during the lease so as to produce a constant periodic rate of interest on the remaining balance of the liability. Leased assets are depreciated in accordance with the company's policy for tangible fixed assets. If there is no reasonable certainty that ownership will be obtained at the end of the lease term, the asset is depreciated over the lower of the lease term

and its useful life. Operating lease payments are recognised as an expense on a straight line basis over the lease term.

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.