1. If the Statement of defence includes an assertion that the patent alleged to be infringed is invalid the Statement of defence shall include a Counterclaim against the proprietor of the patent for revocation of said patent in accordance with Rule 42. The Counterclaim for revocation shall contain:

(a) an indication of the extent to which revocation of the patent is requested;

(b) one or more grounds for revocation, which shall as far as possible be supported by arguments of law, and where appropriate an explanation of the defendant’s proposed claim construction;

(c) an indication of the facts relied on;

(d) the evidence relied on, where available, and an indication of any further evidence which will be offered in support;

(e) an indication of any order the defendant will seek during the interim procedure [Rule 104(e)];

(f) a statement of his position, if any, on the options provided for in Article 33(3) of the Agreement and Rule 37.4;

(g) a list of the documents, including any witness statements, referred to in the Counterclaim for revocation together with any request that all or part of any such documents need not be translated and/or any request pursuant to Rule 262.2 or Rule 262A. Rule 13.2 and .3 shall apply mutatis mutandis; and

(h) insofar as the proprietor of the patent is not claimant in the infringement proceedings, the information required by Rule 13.1(b) and (d) in respect of said proprietor.

2. Where the claimant is not the proprietor or not the only proprietor of the patent concerned, the Registry shall as soon as practicable serve a copy of the Counterclaim for revocation on the relevant proprietor in accordance with Rule 13.1(e) and shall supply a copy of each document referred to in paragraph 1(h). Rule 271 shall apply mutatis mutandis. The proprietor in question shall become a party to the revocation proceedings and shall be treated as defendant in all subsequent proceedings. The proprietor shall provide details pursuant to Rule 13.1(e) if not already provided by the claimant.