1.3. National infringement proceedings

Under Art. 105 EPC, third parties may intervene only if they prove either (a) that proceedings for infringement of the opposed European patent have been instituted against them or (b) that, following a request by that patent's proprietor that they cease the alleged infringement, they have instituted proceedings for a ruling that they are not infringing the patent (G 4/91, OJ 1993, 707). The principle that the assessment of the nature of a procedural act taken by a party before the EPO is to be made with consideration of its actual substance rather than with consideration of its form or name applies equally when deciding whether national infringement proceedings have been commenced (T 188/97).