speed. Mullin v Richards [1998] 1 All ER 920: a fifteen-year-old girl was not negligent when she was play fighting with a friend and a ruler she was fencing with shattered, a splinter flying into the other girl's eye. OLL Ltd v Secretary of State for Transport [1997] 3 All E.R. 897: with particular regard to the duty of care owed by the emergency services. Conduct expected of a reasonable person In the usual case, having established that there is a duty of care, the claimant must prove that the defendant failed to do what the reasonable person ("reasonable professional", "reasonable child") would have done in the same situation. If the defendant fails to come up to the standard, this will be a breach of the duty of care. This is judged by reference to the following factors: What did the defendant know? According to Denning LJ. in Roe v Minister of Health (1954) 2 AER 131, the defendant will only be liable if the reasonable person would have foreseen the loss or damage in the circumstances prevailing at the time of the alleged breach of duty. What was the degree of risk? The greater the risk that serious harm can be inflicted, the greater the precautions that the defendant will be required to take. In Bolton v Stone[1951] A.C. 850, [1951] 1 All E.R. 1078, a cricket club was not negligent when a ball was hit out of the ground and injured the plaintiff, because the likelihood of this occurring was so small that the defendant could not be expected to have taken precautions. In Miller v. Jackson ([1977] QB 966, [1977] 3 WLR 20, [1977] 3 All ER 338 however, the ball was hit out of the ground several times every season. In these circumstances, the club was expected to take precautions. How practical were these precautions? In Wilson v Governor of Sacred Heart Roman Catholic Primary School (1997) EWCA Civ 2644 it was held that a primary school was not negligent in not employing someone to supervise the playground after the close of school hours and until all the children had left. In Haley v London Electricity Board [1964] 3 All ER 185, a blind man fell into a hole in the ground that was indicated by a visual sign. He became deaf as a result. It was held that it was foreseeable that a blind man