The asset within patent rights comprises payments to acquire the right to develop and market Trilostane, the active ingredient of Vetoryl Capsules, for animal health applications in the USA and Canada. The carrying value at 30 June 2018 was £0.1 million with a remaining amortisation period of 0.5 years. The rights to Equidone, which was launched in the US during 2011, has a carrying value of £0.3 million with a remaining amortisation period of 3 years. The in-licensed products within Canada acquired in 2016 had a carrying value of £0.3 million and had a remaining amortisation periods of 8.5 years. During the year, £0.9 million was added to patent rights within EU from Le Vet B.V. On acquisition of Le Vet during the year this and previously acquired patent rights from Le Vet were reclassified to acquired intangibles (£1.7 million).

£0.8 million of the marketing authorisations relate to the Vetivex range of products. Ownership of the marketing authorisations rests with the Group in perpetuity. There are not believed to be any legal, regulatory or contractual provisions that limit their useful lives. Vetivex is an established range of products which are relatively simple in nature and there are a limited number of players in the market. Accordingly, the Directors believe that it is appropriate that the marketing authorisations are treated as having indefinite lives for accounting purposes.

Goodwill is allocated across cash generating units that are expected to benefit from that business combination. Key assumptions made in this respect are given in note 14.

During the year, the contingent consideration in relation to development milestones and sales milestones of the acquired intangibles has been remeasured and to the extent possible remeasured against the intangibles.

In accordance with the disclosure requirements of IAS 38 'Intangible Assets', the components of acquired intangibles are summarised below:

The table below provides further detail on the acquired intangibles and their remaining amortisation period.