Where, as in the present case, a breach of a duty of care is proved or admitted, the burden still lies on the plaintiff to prove that such breach caused the injury suffered: Bonnington Castings Ltd. v. Wardlaw [1956] A.C. 613; Wilsher v. Essex Area Health Authority [1988] A.C. 1074. In all cases the primary question is one of fact: did the wrongful act cause the injury? But in cases where the breach of duty consists of an omission to do an act which ought to be done (e.g. the failure by a doctor to attend) that factual inquiry is, by definition, in the realms of hypothesis. The question is what would have happened if an event which by definition did not occur had occurred. In a case of non-attendance by a doctor, there may be cases in which there is a doubt as to which doctor would have attended if the duty had been fulfilled. But in this case there was no doubt: if the duty had been carried out it would have either been Dr. Horn or Dr. Rodger, the only two doctors at St. Bartholomew's who had responsibility for Patrick and were on duty. Therefore in the present case, the first relevant question is "what would Dr. Horn or Dr. Rodger have done if they had attended?" As to Dr. Horn, the judge accepted her evidence that she would not have intubated. By inference, although not expressly, the judge must have accepted that Dr. Rodger also would not have intubated: as a senior house officer she would not have intubated without the approval of her senior registrar, Dr. Horn.

    Therefore the Bolam test had no part to play in determining the first question, viz. what would have happened? Nor can I see any circumstances in which the Bolam test could be relevant to such a question.

    However in the present case the answer to the question "what would have happened?" is not determinative of the issue of causation. At the trial the defendants accepted that if the professional standard of care required any doctor who attended to intubate Patrick, Patrick's claim must succeed. Dr. Horn could not escape liability by proving that she would have failed to take the course which any competent doctor would have adopted. A defendant cannot escape liability by saying that the damage would have occurred in any event because he would have committed some other breach of duty thereafter. I have no doubt that this concession was rightly made by the defendants. But there is some difficulty in analysing why it was correct. I adopt the analysis of Hobhouse L.J. in Joyce v. Merton, Sutton and Wandsworth Health Authority [1996] 7 Med. L.R. 1. In commenting on the decision of the Court of Appeal in the present case, he said, at p. 20:

 "Thus a plaintiff can discharge the burden of proof on causation by satisfying the court either that the relevant person would in fact have taken the requisite action (although she would not have been at fault if she had not) or that the proper discharge of the relevant person's duty towards the plaintiff required that she take that action. The former alternative calls for no explanation since it is simply the factual proof of the causative effect of the original fault. The latter is slightly more sophisticated: it involves the factual situation that the original fault did not itself cause the injury but that this was because there would have been some further fault on the part of the defendants; the plaintiff proves his case by proving that his injuries would have been avoided if proper care had continued to be taken. In the Bolitho case the plaintiff had to prove that the continuing exercise of proper care would have resulted in his being intubated."

    There were, therefore, two questions for the judge to decide on causation: (1) What would Dr. Horn have done, or authorised to be done, if she had attended Patrick? and (2) If she would not have intubated, would that have been negligent? The Bolam test has no relevance to the first of those questions but is central to the second.

    There can be no doubt that, as the majority of the Court of Appeal held, the judge directed himself correctly in accordance with that approach. The passages from his judgment which I have quoted (and in particular those that I have underlined) demonstrate this. The dissenting judgment of Simon Brown L.J. in the Court of Appeal is based on a misreading of the judge's judgment. He treats the judge as having only asked himself one question, namely, the second question. To the extent that the Lord Justice noticed the first question--would Dr. Horn have intubated?--he said that the judge was wrong to accept Dr. Horn's evidence that she would not have intubated. In my judgment it was for the judge to assess the truth of her evidence on this issue.

    Accordingly the judge asked himself the right questions and answered them on the right basis.

The Bolam test--should the judge have accepted Dr. Dinwiddie's evidence?

    As I have said, the judge took a very favourable view of Dr. Dinwiddie as an expert. He said:

 ". . . I have to say of Dr. Dinwiddie also, that he displayed what seemed to me to be a profound knowledge of paediatric respiratory medicine, coupled with impartiality, and there is no doubt, in my view, of the genuineness of his opinion that intubation was not indicated."

However, the judge also expressed these doubts:

 "Mr. Brennan also advanced a powerful argument--which I have to say, as a layman, appealed to me--to the effect that the views of the defendant's experts simply were not logical or sensible. Given the recent and the more remote history of Patrick's illness, culminating in these two episodes, surely it was unreasonable and illogical not to anticipate the recurrence of a life- threatening event and take the step which it was acknowledged would probably have saved Patrick from harm? This was the safe option, whatever was suspected as the cause, or even if the cause was thought to be a mystery. The difficulty of this approach, as in the end I think Mr. Brennan acknowledged, was that in effect it invited me to substitute my own views for those of the medical experts."

    Mr. Brennan renewed that submission both before the Court of Appeal (who unanimously rejected it) and before your Lordships. He submitted that the judge had wrongly treated the Bolam test as requiring him to accept the views of one truthful body of expert professional advice even though he was unpersuaded of its logical force. He submitted that the judge was wrong in law in adopting that approach and that ultimately it was for the court, not for medical opinion, to decide what was the standard of care required of a professional in the circumstances of each particular case.

    My Lords, I agree with these submissions to the extent that, in my view, the court is not bound to hold that a defendant doctor escapes liability for negligent treatment or diagnosis just because he leads evidence from a number of medical experts who are genuinely of opinion that the defendant's treatment or diagnosis accorded with sound medical practice. In the Bolam case itself, McNair J. stated [1957] 1 W.L.R. 583, 587, that the defendant had to have acted in accordance with the practice accepted as proper by a "responsible body of medical men." Later, at p. 588, he referred to "a standard of practice recognised as proper by a competent reasonable body of opinion." Again, in the passage which I have cited from Maynard's case, Lord Scarman refers to a "respectable" body of professional opinion. The use of these adjectives -responsible, reasonable and respectable--all show that the court has to be satisfied that the exponents of the body of opinion relied upon can demonstrate that such opinion has a logical basis. In particular in cases involving, as they so often do, the weighing of risks against benefits, the judge before accepting a body of opinion as being responsible, reasonable or respectable, will need to be satisfied that, in forming their views, the experts have directed their minds to the question of comparative risks and benefits and have reached a defensible conclusion on the matter.

    There are decisions which demonstrate that the judge is entitled to approach expert professional opinion on this basis. For example, in Hucks v. Cole (a case from 1968 reported in [1993] 4 Med. L.R. 393), a doctor failed to treat with penicillin a patient who was suffering from septic places on her skin though he knew them to contain organisms capable of leading to puerperal fever. A number of distinguished doctors gave evidence that they would not, in the circumstances, have treated with penicillin. The Court of Appeal found the defendant to have been negligent. Sachs L.J. said, at p. 397:

 "When the evidence shows that a lacuna in professional practice exists by which risks of grave danger are knowingly taken, then, however small the risk, the court must anxiously examine that lacuna--particularly if the risk can be easily and inexpensively avoided. If the court finds, on an analysis of the reasons given for not taking those precautions that, in the light of current professional knowledge, there is no proper basis for the lacuna, and that it is definitely not reasonable that those risks should have been taken, its function is to state that fact and where necessary to state that it constitutes negligence. In such a case the practice will no doubt thereafter be altered to the benefit of patients. On such occasions the fact that other practitioners would have done the same thing as the defendant practitioner is a very weighty matter to be put on the scales on his behalf; but it is not, as Mr. Webster readily conceded, conclusive. The court must be vigilant to see whether the reasons given for putting a patient at risk are valid in the light of any well-known advance in medical knowledge, or whether they stem from a residual adherence to out-of-date ideas."

    Again, in Edward Wong Finance Co. Ltd. v. Johnson Stokes & Master [1984] 1 A.C. 296, the defendant's solicitors had conducted the completion of a mortgage transaction in "Hong Kong style" rather than in the old fashioned English style. Completion in Hong Kong style provides for money to be paid over against an undertaking by the solicitors for the borrowers subsequently to hand over the executed documents. This practice opened the gateway through which a dishonest solicitor for the borrower absconded with the loan money without providing the security documents for such loan. The Privy Council held that even though completion in Hong Kong style was almost universally adopted in Hong Kong and was therefore in accordance with a body of professional opinion there, the defendant's solicitors were liable for negligence because there was an obvious risk which could have been guarded against. Thus, the body of professional opinion, though almost universally held, was not reasonable or responsible.

    These decisions demonstrate that in cases of diagnosis and treatment there are cases where, despite a body of professional opinion sanctioning the defendant's conduct, the defendant can properly be held liable for negligence (I am not here considering questions of disclosure of risk). In my judgment that is because, in some cases, it cannot be demonstrated to the judge's satisfaction that the body of opinion relied upon is reasonable or responsible. In the vast majority of cases the fact that distinguished experts in the field are of a particular opinion will demonstrate the reasonableness of that opinion. In particular, where there are questions of assessment of the relative risks and benefits of adopting a particular medical practice, a reasonable view necessarily presupposes that the relative risks and benefits have been weighed by the experts in forming their opinions. But if, in a rare case, it can be demonstrated that the professional opinion is not capable of withstanding logical analysis, the judge is entitled to hold that the body of opinion is not reasonable or responsible.

    I emphasise that in my view it will very seldom be right for a judge to reach the conclusion that views genuinely held by a competent medical expert are unreasonable. The assessment of medical risks and benefits is a matter of clinical judgment which a judge would not normally be able to make without expert evidence. As the quotation from Lord Scarman makes clear, it would be wrong to allow such assessment to deteriorate into seeking to persuade the judge to prefer one of two views both of which are capable of being logically supported. It is only where a judge can be satisfied that the body of expert opinion cannot be logically supported at all that such opinion will not provide the bench mark by reference to which the defendant's conduct falls to be assessed.

    I turn to consider whether this is one of those rare cases. Like the Court of Appeal, in my judgment it plainly is not. Although the judge does not in turn say so, it was implicit in his judgment that he accepted that Dr. Dinwiddie's view was a reasonable view for a doctor to hold. As I read his judgment, he was quoting counsel's submission when he described the view that intubation was not the right course as being "unreasonable and illogical." The appeal of the argument was to the judge "as a layman" not a conclusion he had reached on all the medical evidence. He refused to "substitute his own views for those of the medical experts." I read him as saying that, without expert evidence he would have thought that the risk involved would have called for intubation, but that he could not dismiss Dr. Dinwiddie's views to the contrary as being illogical.

    Even if this is to put too favourable a meaning on the judge's judgment, when the evidence is looked at it is plainly not a case in which Dr. Dinwiddie's views can be dismissed as illogical. According to the accounts of Sister Sallabank and Nurse Newbold, although Patrick had had two severe respiratory crises, he had recovered quickly from both and for the rest presented as a child who was active and running about. Dr. Dinwiddie's view was that these symptoms did not show a progressive respiratory collapse and that there was only a small risk of total respiratory failure. Intubation is not a routine, risk-free process. Dr. Roberton described it as "a major undertaking--an invasive procedure with mortality and morbidity attached--it was an assault." It involves anaesthetising and ventilating the child. A young child does not tolerate a tube easily "at any rate for a day or two" and the child unless sedated tends to remove it. In those circumstances it cannot be suggested that it was illogical for Dr. Dinwiddie a most distinguished expert to favour running what, in his view, was a small risk of total respiratory collapse rather than to submit Patrick to the invasive procedure of intubation.

    Tragic though this case is for Patrick's mother and much as everyone must sympathise with her, I consider that the judge and the Court of Appeal reached the right conclusions on the evidence in this case. I would dismiss the appeal.

LORD SLYNN OF HADLEY

My Lords,

    I have had the advantage of reading in draft the speech prepared by my noble and learned friend, Lord Browne-Wilkinson. I agree with his analysis of the questions which have to be decided in cases of this kind and of the correct approach in law in deciding them. Despite my anxiety as to the result in this particular case, it is to me clear that Hutchinson J. asked the right questions and did not misdirect himself in answering them. He was entitled on all the evidence to accept that of Dr. Dinwiddie. Accordingly, I agree that this appeal must be dismissed.

LORD NOLAN

My Lords,

    I have had the advantage of reading in draft the speech prepared by my noble and learned friend Lord Browne-Wilkinson. For the reasons which he has given, I, too, would dismiss this appeal.

LORD HOFFMANN

My Lords,

    I have had the advantage of reading in draft the speech prepared by my noble and learned friend, Lord Browne-Wilkinson. For the reasons which he has given, I, too, would dismiss this appeal.

LORD CLYDE

My Lords,

    I have had the advantage of reading in draft the speech prepared by my noble and learned friend, Lord Browne-Wilkinson. For the reasons which he has given, I, too, would dismiss this appeal.