No VAT will be charged on the hammer price, but VAT at 15% will be added to the buyer's premium which is invoiced on a VAT inclusive basis.
Cf. John Ayers, Oliver Impey and J.V.G. Mallet, Porcelain for Palaces, The Fashion for Japan in Europe 1650-1750, Oriental Ceramic Society, Exhibition Catalogue (1990), p. 275 no. 321 for an example of the same form.