Expert Insight

Bolam to Montgomery, How the Test for Clinical Negligence Changed

By Prof. Sandip Hindocha
September 25, 2026

Most people who have heard of the Bolam test assume it was swept away by Montgomery v Lanarkshire in 2015. It was not. Bolam is still the test for whether a diagnosis or a course of treatment was negligent, Montgomery only changed the separate question of what a patient has to be told before they agree to it, and a 2023 Supreme Court case has since redrawn the boundary between the two.

Prof. Sandip Hindocha, a Consultant Plastic Surgeon and the UK’s National Lead Forensic Medical Examiner, prepares medical negligence expert reports that have to identify, for every allegation in a case, which of these tests actually applies to it.

In short: the Bolam test, from 1957, asks whether a responsible body of medical opinion would have done what the defendant did, and it still governs diagnosis and treatment decisions today, refined by Bolitho in 1997 so that the opinion relied on has to be logically defensible. Montgomery, from 2015, replaced the old Bolam-based approach to consent with a patient-centred material risk test. McCulloch, in 2023, then clarified that Bolam still decides which treatment options a doctor puts in front of a patient in the first place, Montgomery only governs what has to be said about the options that make that list.

What the Bolam Test Actually Says

Doctor in a white coat using a tablet beside scales of justice and a judge's gavel

Bolam v Friern Hospital Management Committee [1957] 1 WLR 582 gave English law its long-standing test for clinical negligence. Mr Justice McNair directed the jury that a doctor is not negligent if they acted in accordance with a practice accepted as proper by a responsible body of medical opinion, even if other responsible doctors would have taken a different approach.

The effect was that the medical profession largely set its own standard. If a reputable body of colleagues would have done the same thing, the claim failed, regardless of whether a different, equally respectable school of thought existed.

The Bolitho Gloss, a Limit on Blind Deference

Bolitho v City and Hackney Health Authority [1997] UKHL 46 stopped the test being a rubber stamp. The House of Lords held that the body of opinion relied on has to be capable of withstanding logical analysis, the court, not the profession, remains the ultimate arbiter of whether a practice was defensible.

In practice this rarely overturns expert evidence, since a genuinely considered body of professional opinion is usually logical by definition, but it means an expert cannot simply assert that a practice is accepted and expect that to end the enquiry. The reasoning behind the practice has to hold up.

Sidaway, How Bolam Was Applied to Consent

For nearly 30 years after Bolam, the same deferential test was also used to judge what a doctor told a patient before treatment. In Sidaway v Board of Governors of the Bethlem Royal Hospital [1985] AC 871, the House of Lords majority held that how much a patient should be told about the risks of a procedure was, like diagnosis and treatment, a matter of clinical judgement assessed by the Bolam standard.

Lord Scarman dissented, arguing instead for a patient’s right to know material risks regardless of accepted medical practice. His position lost in 1985, but it is essentially the position English law adopted three decades later.

Montgomery, the Shift to Patient Autonomy

Montgomery v Lanarkshire Health Board [2015] UKSC 11 overturned Sidaway. The Supreme Court held that consent is not a question of professional practice at all, it is about a patient’s right to decide what happens to their own body.

The new test requires a doctor to take reasonable care to ensure a patient is aware of any material risk, a risk a reasonable person in the patient’s position would be likely to attach significance to, or one this particular doctor knows this particular patient would attach significance to, along with any reasonable alternative treatments. What matters is the individual patient in front of the doctor, not what a responsible body of colleagues would typically disclose.

	Sidaway (1985 to 2015)	Montgomery (2015 onwards)
Whose standard sets disclosure	The medical profession’s	The reasonable patient’s
Test applied	Bolam, would a responsible body have disclosed this	Material risk, would this patient attach significance to it
Focus	What doctors typically tell patients	What this patient needed to know to decide

Causation After a Failure to Warn, Chester v Afshar

Bronze scales of justice on a marble block with a judge's gavel in the foreground

A separate problem sits behind any consent claim: even if a risk should have been disclosed, the claimant still has to show that disclosure would have made a difference. Chester v Afshar [2004] UKHL 41 shows how far English law has been willing to bend the ordinary rule to make that duty meaningful.

Miss Chester was not warned of a small but recognised risk of significant nerve damage before back surgery. She could not say she would have refused the operation outright, only that she would have delayed it to take further advice. The House of Lords held, by a narrow majority, that this was still enough. Because the injury was so closely tied to the very risk that should have been disclosed, the claim succeeded even though conventional causation, asking what would have happened, could not cleanly answer the question.

This causation question sits alongside, but separately from, the standard of proof discussed in how causation works in complex medico-legal cases, and it is one of the more technical areas where an expert’s evidence needs to be precise about what exactly was and was not disclosed.

McCulloch, the Two-Stage Test Refined

For several years after Montgomery, it was not entirely clear how far patient autonomy reached. Did a doctor have to discuss every treatment a patient might conceivably want to know about, or only a clinically sensible shortlist? McCulloch v Forth Valley Health Board [2023] UKSC 26 answered that question with a two-stage framework. Where a defendant argues that the patient disregarded a risk they did understand, the question becomes one of contributory negligence in a medical claim.

Stage one is deciding which treatments are reasonable alternatives worth putting on the table at all. That remains a matter of clinical judgement, assessed by the Bolam test, a doctor is not negligent for leaving off an option that a responsible body of colleagues would not have considered clinically appropriate. Stage two is Montgomery’s territory, once an option is on that clinically reasonable list, the patient has to be told about it and its material risks in terms that reflect what matters to them.

The Supreme Court was explicit that requiring doctors to discuss every conceivable option, reasonable or not, would encourage defensive medicine rather than better decisions. Bolam decides the menu, Montgomery decides how the menu is explained.

Bolam Is Not Dead, What It Still Governs

Outside consent entirely, Bolam, refined by Bolitho, remains the ordinary test for clinical negligence. Whether a diagnosis was reasonable, whether a surgical technique was appropriate, whether a complication was managed properly once it arose, all of these are still judged by reference to a responsible, logically defensible body of professional opinion, not by what an individual patient would have wanted. That is the test applied to a missed or late diagnosis, which is why cauda equina syndrome negligence claims are argued on what a reasonable clinician should have done with the symptoms recorded at the time.

Montgomery and McCulloch narrowed Bolam’s reach into the consent conversation. They did not touch its role everywhere else, and a surgeon can still successfully defend a claim over the substance of their clinical decision-making on exactly the same basis they could in 1957.

Common Misconceptions About the Two Tests

The most frequent error, in and out of court, is treating Montgomery as a wholesale replacement for Bolam. It replaced Bolam for one specific question, what has to be disclosed about risks and reasonable alternatives, and left it standing everywhere else.

A second, newer error since 2023 is assuming Montgomery lets a patient demand information about any treatment they have heard of. McCulloch confirmed that a doctor only has to discuss options that clear the clinical, Bolam-based bar first.

What This Means for a Medicolegal Expert Report

Doctor writing on a medical form at a desk, with a stethoscope and a judge's gavel in the foreground

A report on a clinical negligence claim has to start by working out which test actually applies to each allegation being made. An allegation that the wrong technique was used, or a complication was mishandled, is a Bolam and Bolitho question, decided against a body of professional opinion. An allegation that a patient was not properly warned, covered in more detail in how informed consent failures are assessed, is a Montgomery and, since 2023, a McCulloch question, decided against what this particular patient needed to know.

Conflating the two is a common and consequential mistake. An expert defending a consent claim by pointing to what a responsible body of surgeons usually tells patients is answering the wrong question, and one attacking a treatment decision by arguing the patient would not have consented if properly informed is doing the same thing in reverse.

Frequently Asked Questions

Did Montgomery v Lanarkshire replace the Bolam test?
Only for consent. Bolam, as refined by Bolitho, still governs whether a diagnosis or treatment decision was negligent. Montgomery replaced it specifically for the question of what risks and alternatives a patient had to be told about.

What is the material risk test from Montgomery?
A risk is material if a reasonable person in the patient’s position would be likely to attach significance to it, or if the doctor is or should be aware that this particular patient would. It is judged from the patient’s perspective, not the profession’s.

What did McCulloch v Forth Valley Health Board decide in 2023?
It clarified that deciding which treatments count as reasonable alternatives is a clinical judgement, assessed by the Bolam test. Only once a treatment clears that bar does Montgomery’s duty to discuss its risks apply.

Can a claim succeed if the patient cannot say they would have refused treatment?
Sometimes, yes. Chester v Afshar established that a claim over an undisclosed risk can succeed even where the patient can only say they would have delayed or sought further advice, not that they would have refused outright.

Does the Bolitho gloss mean courts often reject medical opinion as illogical?
Rarely. Most considered professional opinion is logical by definition, and Bolitho is used sparingly. Its significance is that the court, not the profession, has the final say, not that it frequently overrules medical evidence.