63.15—(1) In a claim for infringement of a registered trade mark the defendant may—
(a)in his defence, challenge the validity of the registration of the trade mark; and
(b)apply by Part 20 claim for—
(i)revocation of the registration;
(ii)a declaration that the registration is invalid; or
(iii)rectification of the register.
(2) Where a defendant applies under paragraph (1)(b) and the relief sought would, if granted, affect an entry in the United Kingdom register, he must serve on the registrar a copy of his claim form.