Half year to 30 June 2018	Half year to 30 June 2017
Revenue	£368.0m	£345.7m
Headline operating profit1	£70.1m	£61.7m
Return on sales2	19.0%	17.8%
Operating profit	£68.2m	£59.4m
Headline profit before taxation1	£69.1m	£60.5m
Profit before taxation	£67.2m	£58.2m
Free cash flow3	£39.4m	£42.1m
Basic headline earnings per share4	27.3p	23.6p
Basic earnings per share	26.6p	22.9p
Interim dividend per share5	5.7p	5.3p

1. Headline operating profit and headline profit before taxation exclude amortisation of acquired intangibles of £1.9m (2017: £2.3m).
2. Return on sales is defined as headline operating profit as a percentage of revenue.
3. Free cash flow is defined as cash generated by operations of £82.6m (H1 2017: £87.3m) less net capital expenditure of £31.0m (H1 2017: £29.7m), net interest paid of £0.9m (H1 2017: £1.2m), and taxation of £11.3m (H1 2017: £14.3m).
4. A detailed EPS reconciliation is provided in note 6.
5. See note 7.