During the period when Lord Blackwell served as a non-executive director of the OFT a company where, at the time, he was also chairman, Interserve plc, became subject to an investigation by the OFT into tender activity in the construction industry prior to him joining the Interserve Board. The investigation was described by the OFT as "one of the largest ever Competition Act investigations". Interserve were found to have engaged in illegal anti-competitive bid rigging activities and were fined a sum of £11,634,750.