Dyslexia is a specific difficulty in learning how to use written notation, not attributable to generally low intellectual performance, emotional difficulties, or external factors. While its existence as a condition in its own right had been suspected for over a century, it is only much more recently that relatively definite tests for its existence have been developed. Even now, no one test can conclusively show its presence or absence. Local education authorities must provide for the special educational needs of children under their care, though it is settled law that the authorities cannot themselves be sued for breach of those duties (X (Minors) v. Bedfordshire C.C.  2 A.C. 633). However, X contains strong dicta that where the plaintiff can demonstrate negligence by particular members of staff, such as educational psychologists, then those members of staff will be personally liable, and the authority will be vicariously liable. Phelps v. Hillingdon L.B.C.  1 W.L.R. 500 raises the question whether this is actually so. The Court of Appeal, reversing Garland J., have now held that there is no such liability. The court heard that even if (contrary to their view) the plaintiff in the case could establish professional negligence by an educational psychologist through failure to diagnose her dyslexia, and that this negligence caused her appreciable harm, none the less she had no cause of action.