6In the judgment under appeal, the General Court summarised the factual background to the dispute in the following terms:1 The applicant … is a French undertaking active on a worldwide level in the building materials sector. It owns 99.99% of the capital of Lafarge Gypsum International SA (“Lafarge Plâtres”), which manufactures and markets various plaster based products including plasterbroad.2 Four main producers are active in the plasterboard sector in Europe: BPB PLC [(“BPB”)], Gebrüder Knauf Westdeutsche Gipswerke KG (“Knauf”), Gyproc Benelux NV (“Gyproc”) and Lafarge Plâtres.3 On the basis of information received, on 25 November 1998 the Commission carried out unannounced inspections at the premises of eight undertakings operating in the plasterboard sector, including Lafarge Plâtres at l’Isle-sur-la-Sorgue (France) and Lafarge in Paris (France). On 1 July 1999, it pursued its investigations at the premises of two other undertakings.4 The Commission then sent requests for information under Article 11 of Regulation No 17… to the various undertakings concerned, including, on 21 September 1999, Lafarge. Lafarge replied thereto on 29 October 1999.5 On 18 April 2001, the Commission initiated the administrative procedure and adopted a statement of objections which it addressed to BPB, Knauf, Lafarge, Etex SA and Gyproc. ……8 On 27 November 2002, the Commission adopted the [contested] decision.9 The operative part of the [contested] decision states:“Article 1BPB … , the Knauf Group, … Lafarge … and Gyproc … have infringed Article 81(1) [EC] by participating in a set of agreements and concerted practices in the plasterboard business.The duration of the infringement was as follows:(a) BPB …: from 31 March 1992, at the latest, to 25 November 1998(b) [the] Knauf [Group]: from 31 March 1992, at the latest, to 25 November 1998(c) … Lafarge …: from 31 August 1992, at the latest, to 25 November 1998(d) Gyproc …: from 6 June 1996, at the latest, to 25 November 1998…Article 3In respect of the infringement referred to in Article 1, the following fines are imposed on the following undertakings:(a) BPB …: EUR 138.6 million(b) … Knauf …: EUR 85.8 million(c) … Lafarge …: EUR 249.6 million(d) Gyproc …: EUR 4.32 million…”10 The Commission found in the [contested] decision that the undertakings concerned participated in a single and continuous agreement which was manifested in the following conduct constituting agreements or concerted practices:— the representatives of BPB and Knauf met in London (United Kingdom) in 1992 and expressed the common desire to stabilise the plasterboard markets in Germany, the United Kingdom, France and the Benelux;— the representatives of BPB and Knauf established, as from 1992, information exchange arrangements, to which Lafarge and subsequently Gyproc acceded, relating to their sales volumes on the German, French, United Kingdom and Benelux plasterboard markets;— the representatives of BPB, Knauf and Lafarge exchanged information, on various occasions, prior to price increases on the United Kingdom market;— in view of particular developments on the German market, the representatives of BPB, Knauf, Lafarge and Gyproc met at Versailles (France) in 1996, Brussels (Belgium) in 1997 and The Hague (Netherlands) in 1998 with a view to sharing out or at least stabilising the German market;— the representatives of BPB, Knauf, Lafarge and Gyproc exchanged information on various occasions and concerted their action on the application of price increases on the German market between 1996 and 1998.11 For the purpose of calculating the amount of the fine, the Commission applied the methods set out in [the 1998] Guidelines … .12 In fixing the starting amount of the fines, determined according to the gravity of the infringement, the Commission initially considered that the undertakings concerned had committed an infringement which was very serious by its very nature in so far as the aim of the practices at issue was to put an end to the price war and to stabilise the market through exchanges of confidential information. The Commission also considered that the practices at issue had had an impact on the market, because the undertakings in question represented almost all plasterboard supply and the various manifestations of the cartel had been put into practice in a market which, in addition, was highly concentrated and oligopolistic. As regards the geographic extent of the relevant market, the Commission considered that the cartel had covered the four main European Community markets, namely Germany, the United Kingdom, France and the Benelux.13 Considering, next, that there was a considerable disparity between the undertakings concerned, the Commission took a differentiated approach, relying for that purpose on the sales turnover for the product concerned on the relevant markets during the last complete year of the infringement. On that basis, the starting amount of the fines was set at EUR 80 million for BPB, EUR 52 million for Knauf and Lafarge and EUR 8 million for Gyproc.14 In order to ensure that the fine had a sufficiently deterrent effect having regard to the size and global resources of the undertakings, the starting amount of the fine imposed on Lafarge was increased by 100%, becoming EUR 104 million.15 In order to take account of the duration of the infringement, the starting amount was then increased by 65% for BPB and Knauf, by 60% for Lafarge and by 20% for Gyproc, the infringement being classified by the Commission as of long duration in the case of Knauf, Lafarge and BPB and of medium duration in the case of Gyproc.16 In respect of aggravating circumstances, the basic amount of the fines imposed on BPB and Lafarge was increased by 50% on account of repeated infringement.17 Next, the Commission reduced by 25% the fine imposed on Gyproc on account of attenuating circumstances, in that it had acted as a destabilising element helping to limit the impact of the cartel on the German market and it was absent from the United Kingdom market.18 Finally, the Commission reduced the amount of the fines by 30% for BPB and by 40% for Gyproc, pursuant to Section D.2 of the Commission Notice on the non-imposition or reduction of fines in cartel cases (OJ 1996 C 207, p. 4; “the Leniency Notice”). Accordingly, the final amount of the fines imposed was EUR 138.6 million for BPB, EUR 85.8 million for Knauf, EUR 249.6 million for Lafarge and EUR 4.32 million for Gyproc.’