"35 New claims in pending actions: rules of court. (1) For the purposes of this Act, any new claim made in the course of any action shall be deemed to be a separate action and to have been commenced— (a) in the case of a new claim made in or by way of third party proceedings, on the date on which those proceedings were commenced; and (b) in the case of any other new claim, on the same date as the original action. (2) In this section a new claim means any claim by way of set-off or counterclaim, and any claim involving either— (a) the addition or substitution of a new cause of action; or (b) the addition or substitution of a new party; and "third party proceedings" means any proceedings brought in the course of any action by any party to the action against a person not previously a party to the action, other than proceedings brought by joining any such person as defendant to any claim already made in the original action by the party bringing the proceedings"