51As regards the third plea in law, alleging a breach of the principle of proportionality, it should first of all be observed that the implementation of Article 11 of Regulation No 17 is subject to compliance with that principle. It is not enough for the information requested to be connected with the subject-matter of the inquiry. What is also necessary is that an obligation imposed on an undertaking to supply an item of information should not constitute a burden on that undertaking which is disproportionate to the requirements of the inquiry.