CPR Part 17 allows any party to amend their Statements of Case before it has been served.
Once a Statements of Case has been served, however, a party can only amend it if they first obtain either the written consent of all the other parties or get the permission of the Court.
An application to amend a Statements of Case by removing, adding or substituting once it has been served must, be made in accordance with CPR Rule 19.4.
This states that nobody may be added or substituted as a claimant unless:
The Commissioners for HM Revenue and Customs may be added as a party to proceedings only if they consent in writing.
CPR19.5 requires that an order for the removal, addition or substitution of a party to must be served on all other parties as well as anyone else affected by the order.
Under CPR19.6, if the Court makes an order for the removal, addition or substitution of a party, it may also give consequential directions regarding:
(a) filing and serving the claim form on any new defendant;
(b) serving relevant documents on the new party; and
(c) the management of the proceedings.