—(1) Where a defendant to an action who makes a counterclaim against the plaintiff alleges that any other person (whether or not a party to the action) is liable to him along with the plaintiff in respect of the subject-matter of the counterclaim, or claims against such other person any relief relating to or connected with the original subject-matter of the action, then, subject to Rule 5(2), he may join that other person as a party against whom the counterclaim is made.
(2) Where a defendant joins a person as a party against whom he makes a counterclaim, he must add that person’s name to the title of the action and serve on him a copy of the counterclaim; and a person on whom a copy of a counterclaim is served under this paragraph shall, if he is not already a party to the action, become a party to it as from the time of service with the same rights in respect of his defence to the counterclaim and otherwise as if he had been duly sued in the ordinary way by the party making the counterclaim.
(3) A defendant who is required by paragraph (2) to serve a copy of the counterclaim made by him on any person who before service is already a party to the action must do so within the period within which, by virtue of Order 18, Rule 2, he must serve on the plaintiff the defence to which the counterclaim is added.
(4) Where by virtue of paragraph (2) a copy of a counterclaim is required to be served on a person who is not already a party to the action, the following provisions of these Rules, namely, Order 10 (except Rule 1(4)), Orders 11 to 13 and Order 70, Rule 3, shall, subject to paragraph (3), apply in relation to the counterclaim and the proceedings arising from it as if —
the counterclaim were a writ and the proceedings arising from it an action; and
the party making the counterclaim were a plaintiff and the party against whom it is made a defendant in that action.
(5) A copy of a counterclaim required to be served on a person who is not already a party to the action must be indorsed with a notice, in Form 12, addressed to that person —
stating that he may enter an appearance in Form 13 and explaining how he may do so.