354In any event, in order to establish infringement, the Commission at least relied on the fact that the applicant had previously been found to have committed an infringement on 23 July 1984 in the Benelux Flat Glass Decision. Having regard to the objective pursued by the Commission in increasing the fine to take account of repeated infringement, namely to deter the offender from committing a similar infringement, the fact that a finding of infringement made 17 years earlier was taken into account to that end cannot infringe the principle of legal certainty. That is all the more the case since in the present case the infringement began on 28 January 1993, that is to say only eight years and six months after the adoption of the Benelux Flat Glass Decision. A policy of penalising repeated infringement can have no practical effect on a person who has committed a first infringement unless the threat of a more severe penalty for a new infringement can be effective over time and thus influence that person's conduct.