Tribunal of Commissioners 25 November 2005
Case Nos CDLA/2879/2004 and CDLA/2899/2004
material. I do not see how there can be something too large to come within the de minimis principle but yet too small to be material.”
Viscount Simonds and Lord Somervell agreed with Lord Reid, and Lords Tucker and Keith delivered speeches to the same effect.
113.Fairchild v Glenhaven Funeral Services Ltd  EWCA Civ 1881,  1 WLR 1052 is another example from the field of tort of the “but for test” being abandoned in favour of some other test in circumstances in which it would have been evidentially impossible to satisfy the “but for test” of causation, given the current state of scientific knowledge.
114.We doubt whether authorities from the law of tort, concerned with the issue whether a disease had been caused by the defendant’s breach of duty, are sufficiently analogous to be of much assistance to us. However, these authorities do illustrate the willingness of the courts, even at common law, to look beyond the traditional test in that field where there are particular evidential difficulties in proving that test.
115.The “material cause” test was advocated by both parties before us. Counsel on behalf of the Secretary of State, on instructions after careful consideration had been given to the implications, proposed a test which appears to be as favourable to claimants as is consistent with the statutory language, and which appears to minimise the difficulties of adjudication which other (less favourable) tests would involve. In these circumstances, we consider we should be slow to reject it. We are persuaded that the test advocated by Mr Kolinsky and Mr Maurici is the correct one.
116.In our judgment, therefore, even if a decision maker or appeal tribunal considers that mental or psychological problems are the substantial cause of a claimant’s walking difficulties, it should award the higher rate of the mobility component if it finds that a physical disorder contributes to the claimant’s inability or virtual inability to walk to more than a minimal extent.
117.That still leaves the issue whether the claimant must currently be suffering from a physical condition which is at the date of the decision a material cause of his inability or virtual inability to walk; or whether it is sufficient that he formerly suffered from a physical condition which has abated but which itself gave rise to a psychological condition which, at the date of the decision, is the only remaining operative cause of the walking difficulty. Mr Maurici submitted that it is not enough that the claimant once suffered from such a physical condition, whereas Mr Kolinsky submitted that it is.
118.We do not consider Harrison to be of any assistance on this issue. In that case, the claimant’s hysteria may have been due to the original injury to his back, sustained when he fell off a crane. However, the medical appeal tribunal found simply that the restriction in the claimant’s ability to walk was not due to a physical cause but was hysterical in origin. It appears to have made no finding one way or the other as to whether the hysteria had originally been caused by the accident. In the penultimate paragraph of his judgment (at page 211G) O’Connor L.J. noted that after the decision of Mr Commissioner Monroe an adjudication officer had awarded mobility allowance on the basis of a report from a psychiatrist giving a physical cause to the hysteria “and thus bringing the man within the statutory provisions”. (See also paragraph 4 of Mr Commissioner Monroe’s decision, referring to a report (not before the medical appeal tribunal, but which may well have been