It was inevitable that, sooner rather than later, the House of Lords would be required to refine the limits of its earlier decision in Fairchild v. Glenhaven Funeral Services Ltd .1 A direct invitation to do so was laid before it in the conjoined appeals in Barker v. Corus (UK) Plc .2 All three appeals in Barker were concerned with the availability, and extent, of recovery by claimants for death due to mesothelioma, caused by exposure to asbestos dust. In two of them,3 the circumstances were the same as they had been in Fairchild . The deceased had worked for a succession of employers, each of whom had, in breach of duty, exposed them to asbestos dust. While it was possible to prove that this exposure had caused the mesothelioma, it was not possible, given the current state of scientific knowledge, to prove which particular period of exposure had done so.4 The decision in Fairchild had already established that a claim could be made against any one of the employers, but the issue which had not been resolved, because it had not been argued, was whether each employer should be held liable in full, ie for the mesothelioma, or only on a proportionate basis. That issue was raised in each of the first two appeals. In the Barker appeal, an added feature was that the deceased had worked for two employers each of whom had negligently exposed him to asbestos dust, but he had also, solely through his own fault,5 exposed himself to asbestos dust during a period of self-employment. This required the House to consider the limits of the “Fairchild exception” and whether the circumstances in Barker fell outside it.