From an English perspective the key question for the future seems to be the extent of the "material contribution to the risk" principle. Clearly it is not every case where the claimant will succeed merely by showing that the defendant's carelessness made a material contribution to the risk of the injury he suffered. Their Lordships are unanimous in approving the result in Wilsher v Essex whilst (rightly in my view) criticising the treatment of the earlier decision of McGhee.

What is the difference between Fairchild and McGhee? The majority approve the distinction drawn by Browne-Wilkinson VC in the CA in Wilsher. The difference is said to be that in McGhee there was a single agent of injury (brick dust) whilst in Wilsher the child's blindness could have been caused by a number of different agents.

I am afraid that I am unconvinced by this. As Lord Hoffmann points out , why should it matter in Fairchild if the claimant had been exposed to two different types of dust by different employers both of which made a material contribution to the risk of cancer? Unfortunately Lord Hoffmann fails to make it clear what he thinks the difference is, simply confining the principle in Fairchild to similar multiple employer cases (para 61 and 73).

A more principled distinction would be that in Fairchild the only possible causes were tortious acts by the defendants. A policy argument could be made for saying that an exception to the 'but for' test is justified in order to prevent him 'falling between two (or more)stools' i.e. being made worse off because there are two or more potential defendants rather than one (cf Baker v Willoughby and Jobling v Associated Dairies). Whilst this distinction appeals, at least to me, it leads to the conclusion that McGhee, the most important case relied upon in Fairchild, is wrongly decided at least as now interpreted. In McGhee one (indeed the probable) cause of the dermatitis was the (non-tortious) period during working hours.

A further difficulty with the distinction I have set out is the following case.

Suppose the victim was employed by D1 for six years during which he is exposed to asbestos. He is then employed for one day by D2. He then develops mesothelioma. Surely on the balance of probabilities the disease was caused by D1? Can a claim still be made against D2 for the full loss? On the distinction between Wilsher and Fairchild adopted by the majority of their Lordships the answer is yes.