1. Delaying detailed substantiation of the ground of inventive step raised in the notice of opposition to the last moment of opposition proceedings should be avoided if possible since it creates an unexpected situation for the other parties and the opposition division.

2. However, in the special case where an inventive step argument is based on the same document as the novelty argument, and the novelty of the features in question cannot be answered with a simple yes or no, but depends on how the document is interpreted as a whole, it may be difficult if not impossible for an opponent to argue lack of inventive step without a precise statement of how the document is understood, and the features actually found to be different by the opposition division.

3. In order to guarantee the right to be heard (Article 113(1) EPC), there should in any case be an explicit step during oral proceedings, recorded in the minutes, giving an opponent an opportunity to comment on inventive step on the basis of the opposition division's finding with respect to novelty before deciding against the opponent.

(See points 13 to 15 of the reasons).