Half year to 30 June 2017	Half year to 30 June 2016
Revenue	£345.7m	£291.0m
Headline operating profit1	£61.7m	£49.3m
Return on sales2	17.8%	16.9%
Operating profit	£59.4m	£47.1m
Headline profit before taxation1	£60.5m	£48.1m
Profit before taxation	£58.2m	£45.9m
Headline operating cash flow3	£59.9m	£38.0m
Operating cash flow4	£57.6m	£33.7m
Net cash/(debt)	£17.7m	£(5.5)m
Basic headline earnings per share5	23.6p	18.3p
Basic earnings per share5	22.9p	17.5p
Interim dividend per share6	5.3p	5.0p

1. Headline operating profit and headline profit before taxation are before amortisation of acquired intangibles of £2.3m (2016: £2.2m).
2. Return on sales is defined as headline operating profit as a percentage of revenue.
3. Headline operating cash flow is defined as operating cash flow before cash flow relating to restructuring of £2.3m (2016: £4.3m).
4. Operating cash flow is defined as cash generated by operations of £87.3m (2016: £64.7m) less net capital expenditure of £29.7m (2016: £31.0m).
5. A detailed reconciliation is provided in note 5.
6. See note 6.