Late amendment refused in clinical negligence cauda equina claim
Williams v Wilkinson [2026] EWHC 1088 (KB)
On 8 May 2026, Mr Justice Cotter refused the Claimant’s application to amend her Particulars of Claim, to rely on further witness and expert evidence, and to vacate the imminent trial in a clinical negligence claim arising from a delayed diagnosis of Cauda Equina Syndrome (“CES”). The judgment adds to the growing body of first-instance authority on very late amendments under CPR 17.3, and is a salutary reminder of the discipline required when pleading causation in CES claims where breach is admitted but the counterfactual is anything but straightforward.
Background
On 14 February 2020, the Claimant attended the Defendant osteopath between 5 and 6 pm. She presented with red-flag features of CES, including perineal numbness and impaired perianal sensation. The Defendant failed to advise immediate attendance at A&E – a breach of duty which, by the time of the application, had been conceded. The Claimant returned home, deteriorated, and rang NHS 111 at 9.27 pm. An ambulance attended at around 11.10 pm and she arrived at the Royal Sussex County Hospital (“RSCH”) at 00.08 on 15 February. After a five-hour wait for MRI, a neurosurgical plan was made at 05.45 “for theatre this morning”, but surgery did not in fact take place until 16.10, another patient having been prioritised for emergency burr hole evacuation of a chronic subdural haematoma.
The pleaded case on causation was that, but for the Defendant’s failure to send the Claimant to A&E that evening, surgery would have been performed sooner and her residual deficit avoided. The Defendant’s position was that the timing of surgery would have been the same in any event; and that the residual symptoms were attributable to intra-operative damage rather than to delay. The schedule of loss was pleaded at £873,395 against a counter-schedule of £86,571.
The application
With trial fixed for 15 June 2026, the Claimant applied for permission to: (a) amend the Particulars of Claim; (b) rely on a further witness statement from the Claimant; (c) rely on the witness statement of her solicitor, dated 2 April 2026; (d) rely on further expert evidence from her urology and pain management experts; and (e) rely on further expert evidence from her spinal expert. It was accepted that, if granted, the application would vacate the trial date.
The proposed amendment reformulated the counterfactual into two pathways. The primary case was that the Claimant would in fact have gone home (because she did not drive and needed to collect her son from nursery) and then called 999 or 111, with the result that the same ambulance sequence would have unfolded, surgery taking place during the night or, alternatively, first thing in the morning at around 09.00. The alternative pathway was that, had she gone directly to A&E, she would have been scanned out of hours and operated on by 09.00, some seven hours earlier than 16.10.
Decision
Cotter J refused permission on each head. Applying the framework in Quah Su-Ling v Goldman Sachs International [2015] EWHC 759 (Comm), the application was “very late”: a heavy burden lay on the Claimant to demonstrate both the strength of the proposed new case and a good explanation for the delay, and neither limb was made out.
The judge accepted that the existing pleaded case was, on the Claimant’s own evidence, untenable; but the proposed reformulation was not the answer. The new counterfactual required the Court to make assumptions about a chain of events – when NHS 111 (or 999) would have been contacted, how quickly an ambulance would have arrived, when an MRI would have been undertaken at RSCH, and how the 05.45 morning handover decision would have unfolded – which the evidence simply did not address. Neither the proposed pleading nor the joint statement grappled with the registrar’s 05.45 decision or the prioritisation that occurred at the morning handover. The amendment was not bound to fail, but its prospects were “very uncertain”. Cotter J reiterated that there is no onus on a defendant to plead a counterfactual: the burden of proving causation, including the realistic alternative sequence of events, rests squarely on the claimant.
On delay, the Claimant had been on notice of the deficiencies in her pleaded case for many months. Mr Jackowski’s report for the Defendant in October 2025 had directly raised the factual causation battleground (which A&E the Claimant would have attended, and the realistic timetable thereafter), and Mr Clarke’s evidence for the Claimant had not addressed why surgery had been delayed at RSCH after the 05.45 plan. As Counsel for the Claimant conceded in oral submissions, the Claimant’s team should have analysed this issue and taken further instructions from the Claimant much earlier; they did not. No adequate explanation for the delay was offered.
Weighing the overriding objective, the prejudice to the Defendant, the Court and other court users in losing a trial date outweighed the injustice to the Claimant of being held to her existing pleading.
Comment
Although the Quah principles are well established, Williams shows clearly how those principles bite in the clinical negligence context. Three points are worth flagging.
An admission of breach is the beginning, not the end, of the causation enquiry in CES claims. The counterfactual in delayed-CES cases almost always involves a granular reconstruction of the patient pathway: the 111 call, ambulance response, ED triage, imaging, on-call neurosurgical decision-making and theatre availability. Each link in that chain must be evidenced. A holding pleading that simply asserts earlier surgery would have produced a better outcome will be exposed as untenable when tested against the defendant’s expert and the contemporaneous records.
Williams reinforces that the obligation to put one’s causation house in order is the Claimant’s, and the Court will not strain to allow late re-pleading; even where the underlying breach is admitted and the sums in issue are substantial. The disparity between the parties’ quantum figures (£873,395 against £86,571) did not save the application; if anything, it underscored why a properly evidenced pleading at an early stage was essential.
The judgment is also a reminder that the trial window itself is a protected interest. Cotter J’s emphasis on prejudice to other court users echoes the line of authority running from Quah through CIP Properties (AIPT) Ltd v Galliford Try [2015] EWHC 1345 (TCC) and into more recent first-instance refusals: where an amendment will vacate a fixed trial, the threshold is high and self-inflicted delay will often be fatal.
The practical lesson is straightforward. In delayed-diagnosis CES claims – and indeed in any clinical negligence claim where the counterfactual depends on hospital systems and timings – the claimant team should interrogate the proposed counterfactual at the letter of claim stage, stress-test it against the defendant’s likely expert response, and re-plead promptly if the pleaded case will not hold. By the time trial is weeks away, the door, as Williams shows, will usually be closed.
