Inventive step3.1 Document D1 indisputedly represents the closest prior art.3.2 The Board agrees with the analysis of D1 made by the opposition division (see points 7 to 9 of the decision under appeal), according to which D1 does not disclose, in particular, the following steps of claim 1 of the patent in suit:pressurizing said packs to a low pressure with an inert forming gas such as argon, said