It is not uncommon for a claimant who has issued a professional negligence claim to realise, once limitation has expired, that he has sued the wrong defendant. One potential escape route for claimants in this predicament was shut down on Friday 6 February 2026 by the Court of Appeal in the conjoined appeals in Adcamp LLP v Office Properties and BDB Pitmans v Lee [2026] EWCA Civ 50.
In this article, Helen Evans KC explains what has happened and why.
In professional liability claims, the “wrong defendant” problem often occurs because a professional firm has been superseded by an LLP and the claimant does not know which entity to sue. Claimants have tried a variety of routes to solve their problem- including CPR 19.6.3(a) and arguments based on novation. However, these can either involve satisfying stringent requirements or grappling with tricky insurance coverage consequences.[1]
The potential alternative escape route at issue in the Court of Appeal in Adcamp was CPR 19.6(3)(b). This allows substitution where a claim cannot properly be carried on against a party unless the new one is substituted. Although that power sounds broad, the issue is in the “small print”: it can only be used where the new claim is the same as the old one.
This prompts two questions:
- How can a claim against a different party ever be the “same”?
- If it cannot, then what is the point of CPR 19.6(3)(b)?
To support their claim for substitution, the claimants in Adcamp prayed in aid a line of cases where Insolvency Act 1986 proceedings had accidentally being brought by liquidators rather than a company (or vice versa). The courts had taken a relatively permissive approach to permitting substitution in that context. The claimants therefore suggested that a similar approach should be applied to their predicament. The Court of Appeal disagreed. It regarded claims under the Insolvency Act as standing apart from others (because that Act merely creates a merely procedural device whereby a liquidator can pursue a company’s cause of action).
Outside that context, it is much harder to find a route through via CPR 19.6(3)(b).
As to when a claim is the “same” as a previous one or not, the Court of Appeal suggested in Adcamp that the test was whether the “essential facts to be averred” were identical.
The Court acknowledged that consequently it was hard to see when CPR 19.6(3)(b) would in fact permit substitution of a new defendant. It suggested that it might be applicable if, after a claim was issued, the claimant’s interest in, or the defendant’s liability for, a claim was transferred to a new party (e.g. by assignment or novation). However, there is already a specific rule for that particular issue (at CPR 19.6(3)(c)).
So where does this leave CPR 19.6(3)(b)? In a case where a claimant has sued the wrong defendant in a professional negligence claim, the answer seems to be “probably redundant”.
The Court of Appeal accepted that this outcome creates something of an incoherent picture overall. Under an alternative rule mentioned above, CPR 19.6(3)(a), claimants can still substitute if they have made a mistake of fact about which professional carried out work for them, but not a mistake of law over who is liable for it.
Now they cannot rely on CPR 19.6(3)(b) to rescue them in the latter situation. Is this logical? The Court of Appeal certainly felt its hands were tied and concluded: “If it needs putting right, it is for the Supreme Court to do so”.
It remains to be seen what the Supreme Court will in fact do: permission to appeal is understood to have been granted by the Court of Appeal. Until then, the CPR 19.6(3)(b) route has been closed off.
© Helen Evans KC, 4 New Square Chambers, April 2026
This article is not intended as a substitute for legal advice. Advice about a given set of facts should always be taken.
[1] See further Professional Liability, Regulatory and Coverage Update: what happened in 2025 and what’s next in 2026? – 4 New Square Chambers
