246It also follows from Regulation No 4064/89, however, that the system for the control of concentrations which it establishes is designed to allow the Commission to exercise effective control of all concentrations from the point of view of their effect on the structure of competition (seventh recital) and that the effectiveness of that system is ensured by the introduction of ex ante control of the effects of concentrations with a Community dimension. It follows from the 17th recital to and also from Article 4 and Article 7(1) of Regulation No 4064/89 that the effectiveness of that control rests on a duty for undertakings to notify such concentrations in advance and to suspend their implementation until the Commission has adopted a decision declaring them compatible with the common market. Furthermore, the limitations on the possibility of granting a derogation from the obligation to suspend the concentration laid down in Article 7 and the severity of the penalties provided for in Article 14(2)(b) of Regulation No 4064/89 in the event of a breach of that obligation confirm the fundamental importance which the legislature placed on the obligation to suspend the concentration in the context of the control of concentrations, an approach which is justified in so far as the implementation of a concentration affects the structure of the market and may render more difficult the decisions whereby the Commission seeks, where necessary, to restore effective competition. In the light of that context, the Commission is correct to maintain that the ex post analysis of the lack of effect of a concentration on the market cannot reasonably be a decisive factor for the characterisation of the gravity of the breach of the system of ex ante control.