opposition is rejected as inadmissible. If an opposition is deemed not to have been filed, any opposition fee which has been paid is refunded. In contrast, if an opposition is rejected as inadmissible, an already paid opposition fee is not refunded. Straw man An opposition may be filed by a straw man to conceal the identity of the party actually interested in having the patent revoked. A strawman is "a party acting on behalf of another person." In 1999, the Enlarged Board of Appeal held that the use of a straw man did not render the opposition inadmissible unless "the involvement of the opponent is to be regarded as circumventing the law by abuse of process." Filing of an opposition in common by a group of persons An opposition may be jointly filed by more than one natural or legal persons. Such an opposition is admissible upon payment of a single opposition fee. It must, however, be "clear throughout the procedure who belongs to the group of common opponents". Substantive examination If the opposition is admissible, the Opposition Division examines the grounds for opposition as to their merits. In that examination, the Opposition Division is not limited "to the facts, evidence and arguments provided by the parties and the relief sought" but it examines "the facts of its own motion". The Opposition Division may even, of its own motion, raise a new ground for opposition that the opponent(s) did not raise in their notice of opposition. The Opposition Division may do so "if there are clear reasons to believe that such grounds are relevant and would in whole or in part prejudice the maintenance of the European patent", the underlying aim being to avoid "the maintenance of European patents which are invalid". The patent proprietor also has the opportunity to reply to the grounds of opposition. That is, the proprietor may submit arguments and, to a certain extent, amendments in reply thereto. Thus, in view of the grounds of opposition, and in view for instance of a prior art document introduced into the proceedings by the opponent, the proprietor may amend the patent, i.e. the description, claims, and drawings thereof, although amendments may not be filed as of right at any stage during the opposition proceedings. The patent proprietor is master of its own patent in that the decision to amend or not, and how to amend the patent, is