(3)In proceeding against any person for any act in contravention of section 22, it shall be a defence to prove that at the time of such contravention there was in force a contract relating to the registered design and containing a condition declared unlawful by this section:Provided that this sub-section shall not apply if the plaintiff is not a party to the contract and proves to the satisfaction of the court that the restrictive condition was inserted in the contract without his knowledge and consent, express or implied.
