Shares in
subsidiary
undertakings
£m
Cost
At 1 July 2017459.7
Additions199.7
At 30 June 2018659.4
Impairment
At 1 July 201712.2
Charge for the period
At 30 June 201812.2
Net book value
At 30 June 2018647.2
At 30 June 2017447.5

A list of subsidiary undertakings is given in note (xii). During the year, the Company invested in Dechra Investments Limited and Dechra Finance Ireland DAC, both wholly owned subsidiaries.