The defendant, Dr Scott, negligently misdiagnosed the plaintiff's malignant cancer, (non-Hodgkin Lymphoma) stating it to be a benign collection of fatty tissue and thus no further treatment was needed.

This had the effect of delaying Mr Gregg's treatment by nine months, reducing his chances of surviving ten years from 42% to 25%.

Damages were not recoverable because Mr Gregg failed to prove on the balance of probabilities that Dr Scott's negligence resulted in the loss of a chance of recovery.

Although Lord Hoffman noted cases in other jurisdictions that gave effect to loss of a chance claims where the plaintiff was unable to meet the factual causation standards of liability, such as in the Irish case of Philp v Ryan, he concluded that these were contrary to overriding UK authorities that would be inappropriate to 'abandon:' I respectfully agree.

And in my opinion, the various control mechanisms proposed to confine liability for loss of a chance within artificial limits do not pass this test.

But a wholesale adoption of possible rather than probable causation as the criterion of liability would be so radical a change in our law as to amount to a legislative act.

In company with my noble and learned friends Lord Phillips of Worth Matravers and Baroness Hale of Richmond, I think that any such change should be left to Parliament.

The law should recognise that Mr Gregg's prospects of recovery had he been treated promptly, expressed in percentage terms of likelihood, represent the reality of his position so far as medical knowledge is concerned.

It cannot be right to adopt a procedure having the effect that, in law, a patient's prospects of recovery are treated as non-existent whenever they exist but fall short of 50%.

The law should not, by adopting the all-or-nothing balance of probability approach, assume certainty where none in truth exists: see Deane J in Commonwealth of Australia v Amann Aviation Pty Ltd (1991) 66 ALJR 123, 147.

The difference between good and poor prospects is a matter going to the amount of compensation fairly payable, not to liability to make payment at all.

As Dore J said in Herskovits v Group Health Cooperative of Puget Sound (1983) 664 P 2d 474, 477: 'To decide otherwise would be a blanket release from liability for doctors and hospitals any time there was less than a 50 per cent chance of survival, regardless of how flagrant the negligence.'

The way ahead must surely be to recognise that where a patient is suffering from illness or injury and his prospects of recovery are attended with a significant degree of medical uncertainty, and he suffers a significant diminution of his prospects of recovery by reason of medical negligence whether of diagnosis or treatment, that diminution constitutes actionable damage.

But the present state of the law on this aspect of medical negligence, far from meeting present-day requirements of fairness, generates continuing instinctive judicial unease, exemplified in this country post-Hotson by Latham LJ's dissenting judgment in the present case, and observations of Andrew Smith J in Smith v National Health Service Litigation [2001] Lloyd's Med Rep 90 and the Court of Appeal in Coudert Brothers v Normans Bay Ltd (27 February 2004, unreported).