Common employment
5.—(1)  It shall not be a defence to an employer who is sued in respect of personal injuries caused by the negligence of a person employed by him, that that person was at the time the injuries were caused in common employment with the person injured.
(2)  Any provision in a contract of service or apprenticeship, or in an agreement collateral thereto shall be void in so far as it would have the effect of excluding or limiting any liability of the employer in respect of personal injuries caused to the person employed or apprenticed by the negligence of persons in common employment with him.
(3)  In this section, “personal injury” includes any disease and any impairment of a person’s physical or mental condition, and “injured” shall be construed accordingly.