Judgements and key sources of estimation uncertaintyThe preparation of the financial statements requires management to make judgements, estimates and assumptions that affect the amounts reported. These estimates and judgements are continually reviewed and are based on experience and other factors, including expectations of future events that are believed to be reasonable under the circumstances.Income taxThe taxation expense represents the aggregate amount of current and deferred tax recognised in the reporting period. Tax is recognised in profit or loss, except to the extent that it relates to items recognised in other comprehensive income or directly in equity. In this case, tax is recognised in other comprehensive income or directly in equity, respectively.Current tax is recognised on taxable profit for the current and past periods. Current tax is measured at the amounts of tax expected to pay or recover using the tax rates and laws that have been enacted or substantively enacted at the reporting date.Deferred tax is recognised in respect of all timing differences at the reporting date. Unrelieved tax losses and other deferred tax assets are recognised to the extent that it is probable that they will be recovered against the reversal of deferred tax liabilities or other future taxable profits. Deferred tax is measured using the tax rates and laws that have been enacted or substantively enacted by the reporting date that are expected to apply to the reversal of the timing difference.Impairment of fixed assetsA review for indicators of impairment is carried out at each reporting date, with the recoverable amount being estimated where such indicators exist. Where the carrying value exceeds the recoverable amount, the asset is impaired accordingly. Prior impairments are also reviewed for possible reversal at each reporting date. For the purposes of impairment testing, when it is not possible to estimate the recoverable amount of an individual asset, an estimate is made of the recoverable amount of the cash-generating unit to which the asset belongs. The cash-generating unit is the smallest identifiable group of assets that includes the asset and generates cash inflows that largely independent of the cash inflows from other assets or groups of assets.For impairment testing of goodwill, the goodwill acquired in a business combination is, from the acquisition date, allocated to each of the cash-generating units that are expected to benefit from the synergies of the combination, irrespective of whether other assets or liabilities of the company are assigned to those units.Government grantsGovernment grants are recognised at the fair value of the asset received or receivable. Grants are not recognised until there is reasonable assurance that the company will comply with the conditions attaching to them and the grants will be received.Government grants are recognised using the accrual model and the performance model.Under the accrual model, government grants relating to revenue are recognised on a systematic basis over the periods in which the company recognises the related costs for which the grant is intended to compensate. Grants that are receivable as compensation for expenses or losses already incurred or for the purpose of giving immediate financial support to the entity with no future related costs are recognised in income in the period in which it becomes receivable.Grants relating to assets are recognised in income on a systematic basis over the expected useful life of the asset. Where part of a grant relating to an asset is deferred, it is recognised as deferred income and not deducted from the carrying amount of the asset.Under the performance model, where the grant does not impose specified future performance-related conditions on the recipient, it is recognised in income when the grant proceeds are received or receivable. Where the grant does impose specified future performance-related conditions on the recipient, it is recognised in income only when the performance-related conditions have been met. Where grants received are prior to satisfying the revenue recognition criteria, they are recognised as a liability.Financial instrumentsFinancial liabilities and equity instruments are classified according to the substance of the contractual arrangements entered into. An equity instrument is any contract that evidences a residual interest in the assets of the entity after deducting all of its financial liabilities.Where the contractual obligations of financial instruments (including share capital) are equivalent to a similar debt instrument, those financial instruments are classed as financial liabilities. Financial liabilities are presented as such in the balance sheet. Finance costs and gains or losses relating to financial liabilities are included in the profit and loss account. Finance costs are calculated so as to produce a constant rate of return on the outstanding liability.Where the contractual terms of share capital do not have any terms meeting the definition of a financial liability then this is classed as an equity instrument. Dividends and distributions relating to equity instruments are debited direct to equity.Defined contribution plansContributions to defined contribution plans are recognised as an expense in the period in which the related service is provided. Prepaid contributions are recognised as an asset to the extent that the prepayment will lead to a reduction in future payments or a cash refund.When contributions are not expected to be settled wholly within 12 months of the end of the reporting date in which the employees render the related service, the liability is measured on a discounted present value basis. The unwinding of the discount is recognised as a finance cost in profit or loss in the period in which it arises.