(1) This rule applies if—
(a) a person has been incorrectly or unnecessarily included as a co-plaintiff in a proceeding; and
(b) the defendant has set up a counterclaim or set–off.
(2) The defendant may get the benefit of the counterclaim or set-off by proving the claim or set-off against the parties other than the co-plaintiff.
(3) The defendant's entitlement under subrule (2) is not affected by—
(a) the inclusion of the co-plaintiff; or
(b) any proceeding resulting from the inclusion.