How statements of case are clarified and amended, and how parties are added or substituted — and the stricter rules that apply once a limitation period has expired.
Pleadings rarely survive litigation unchanged, and the rules draw a sharp line between routine tidying and changes that prejudice an opponent or revive a stale claim. The chapter starts with requests for further information under Part 18, the mechanism for pinning down an unclear statement of case, including the written request that should precede any application. It then works through amendment under Part 17 — when permission is needed, the factors the court weighs and who bears the costs — before examining the tighter regime after limitation has expired, where everything turns on whether the amendment merely particularises an existing claim or introduces a new cause of action. Finally it covers adding and substituting parties under Part 19, both in the ordinary course and out of time, where the addition must be necessary or rest on a genuine mistake as to name.
