20.2.—(1) This Part applies to—
(a)a counterclaim by a defendant against the claimant or against the claimant and some other person;
(b)an additional claim by a defendant against any person (whether or not already a party) for contribution or indemnity or some other remedy; and
(c)where an additional claim has been made against a person who is not already a party, any additional claim made by that person against any other person (whether or not already a party).
(2) In these Rules—
(a)“additional claim” means any claim other than the claim by the claimant against the defendant; and
(b)unless the context requires otherwise, references to a claimant or defendant include a party bringing or defending an additional claim.