No VAT will be charged on the hammer price, but VAT at 17.5% will be added to the buyer's premium which is invoiced on a VAT inclusive basis.
See: von Dewitz et al, Silber und Salz, pp. 522-547; Goldschmidt & Naef, The Truthful Lens, p. 25, p. 213, no. 120 and pp. 101, 124 (illus.); and Hamber, A Higher Branch of Art, pp. 225-229.