Non-underlying items charged to operating profit comprise:

2017
£000
2016
£000
Amortisation of acquired intangibles
— classified within selling, general and administrative expenses29,00320,149
— classified within research and development expenses11,441
Impairment of investments602
Impairment of acquired intangibles and associated deferred consideration1,675
Fair value uplift of inventory acquired through business combinations4,2256,070
Rationalisation costs8091,581
Expenses relating to acquisition activities2,0553,889
48,13533,364

Amortisation of acquired intangibles reflects the amortisation of the fair values of future cash flows recognised on acquisition in relation to the identifiable intangible assets acquired.

Impairment of investments relates to the impairment of the investment in Jaguar Animal Heath Inc.

Impairment of acquired intangibles and associated deferred consideration includes the impairment of a US generic pharmaceutical product following the acquisition of Putney Inc., as Putney have already developed a similar product. It also includes the impairment of an acquired intangible due to the cessation of sales following a competitor registration in the US.

The fair value uplift of inventory acquired through business combinations is recognised in accordance with IFRS 3 'Business Combinations' to record the inventory acquired at fair value and its subsequent release into the income statement.

Rationalisation costs relate to the integration and restructuring programmes implemented subsequent to acquisitions or the reorganisation of internal functions.

Expenses relating to acquisition activities includes legal and professional fees incurred during the acquisitions of Apex (£1.6 million) and Medical Ethics (£0.4 million).