Under R. 89 in conjunction with R. 76 EPC, the notice of intervention must give the grounds for the intervention, and the facts and evidence submitted to substantiate them.

In T 1659/07 the board found that the substantiation requirement under R. 89(2) EPC in conjunction with R. 76(2)(c) EPC was met by a reference to an existing statement of grounds for appeal or notice of opposition. The purpose of the requirement was to ensure that the intervener's arguments could be objectively understood, i.e. that the intervener's position was set out clearly enough that both the patentee and the opposition division or board of appeal could identify the reasons for the intervention. Reference to the arguments of another opponent already on file was sufficient to that end. Accordingly, an intervener need not repeat those arguments in detail or contest the patent on the basis of new, independent reasoning or facts.