In T 1649/10, the opposition division held that the subject-matter of claim 1 of the patent as granted did not involve an inventive step and decided to maintain the patent as amended. On appeal, appellant I (opponent) raised the issue of the admissibility of appellant II's (patentee) appeal, invoking, among other things, a lack of substantiation. In this regard, the board held that the mere indication by appellant II that the subject-matter of granted claim 1 was inventive, starting from document D4 as the closest prior art, whereas the impugned decision based its analysis on a combination of D10 as the closest prior art and document D4, did not fulfil the requirements of R. 99(2) EPC as to the necessity for the appellant to indicate the reasons for setting aside the decision. The board was thus not in a position to recognise in the reasoning put forward by appellant II, which relied on D4 as the closest prior art, why the reasoning of the opposition division, which relied on document D10 as closest prior art, had to be rejected. The appeal filed by appellant II was, hence, rejected as inadmissible. Its role in the appeal proceedings was then that of a party as of right under Art. 107 EPC.