Half year to 30 June
	2018 £m	2017 £m
Revenue	368.0	345.7
Headline operating profit	70.1	61.7
Amortisation of acquired intangible fixed assets	(1.9)	(2.3)
Operating profit	68.2	59.4
Net finance charge	(1.0)	(1.2)
Profit before taxation	67.2	58.2
Taxation	(16.4)	(14.6)
Profit for the period	50.8	43.6

Group revenue was £368.0m, an increase of 6.4% at actual exchange rates and 8.7% at constant currency. Headline operating profit for the six months increased by 14% to £70.1m (H1 2017: £61.7m), and return on sales increased to 19.0% (H1 2017: 17.8%). Headline operating profit at constant currency increased by 15% to £71.2m. Once again, increases in input costs were more than recovered via price increases and the Group maintained a strong focus on cost control and operational efficiency. Statutory operating profit grew to £68.2m (H1 2017: £59.4m).