The following items have been included in arriving at profit before taxation of continuing operations:

2018
£m
2017
£m
Cost of inventories recognised as an expense140.4147.7
Impairment of inventories included in above figure2.00.9
Depreciation of property, plant and equipment
— owned assets4.84.9
Amortisation of intangible assets56.642.4
Loss on disposal of property, plant and equipment0.2
Loss on disposal of intangible assets0.3
Impairment of intangible assets — underlying0.1
(Release)/recognition of impairment of receivables(0.1)0.4
Operating lease rentals payable2.83.0
Research and development expenditure as incurred18.315.0
Auditors' remuneration1.40.7
Analysis of total fees paid to the Auditors:
Audit of these financial statements0.40.2
Audit of financial statements of subsidiaries pursuant to legislation0.50.4
Other assurance services - transaction services0.50.1
Total fees paid to Auditors1.40.7

Included within research and development expenditure is £0.25 million to secure the worldwide rights for an equine gastro intestinal formulation from NewMarket Pharmaceuticals LLC which we plan to develop to registration through our R&D team.