(2)Where an offence under this Act is committed by a company or body of persons, corporate or unincorporate, every person who at the time of the commission of that offence was the secretary, manager, director or other principal officer of that company or body of persons, shall be deemed to be guilty of that offence, unless he proves that the offence was committed without his knowledge and that he exercised all such diligence to prevent the commission of that offence as he ought to have exercised, having regard to the nature of his functions in such capacity and to all the other circumstances.