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—
In this section a new claim means any claim by way of set-off or counterclaim, and any claim involving either—
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.
Rules of court may provide for allowing a new claim to which subsection (3) above applies to be made as there mentioned, but only if the conditions specified in subsection (5) below are satisfied, and subject to any further restrictions the rules may impose.
The conditions referred to in subsection (4) above are the following—
The addition or substitution of a new party shall not be regarded for the purposes of subsection (5)(b) above as necessary for the determination of the original action unless either—
Subsections (3) to (7) above shall apply in relation to a new claim made in the course of third party proceedings as if those proceedings were the original action, and subject to such other modifications as may be prescribed by rules of court in any case or class of case.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .