Explain the elements important in assessing 'breach of duty' in the tort of negligence.

The key point to note about breach of duty is that it is assessed objectively - what action or inaction would be expected of 'the reasonable man' in the position of the defendant. Reasonableness is assessed in all the circumstances, and only limited features of the individual defendant will be taken into account. These include: "professionals" (including trainees) Wilsher v Essex, and children Mullin v Richards. The Bolam test allows for discharging one's duty by reference to a responsible body of opinion from within the person's profession, even where this is not a majority view, subject to an underlying requirement of 'logically defensible' (Bolitho v City & Hackney Health Authority)

Within this objective test, there are, variously, three or four distinct categories relevant to the assessment. The uncontroversial first two are gravity of harm (The Wagon Mound No.2 ) and extent of risk (Bolton v Stone). The basic principles expressed are that it is unreasonable to risk acting where that risk or the potential danger is unacceptably high. The latter element is more complex, involving consideration of policy. It is known variously as costs of prevention, public policy, utility, or simply by reference to 'worthwhile' actions. A paradigm case is that of Latimer v AEC, where it was decided that it would not be reasonable to close a factory that had been flooded, given that the defendant had put up warnings and laid down sawdust. These elements are considered together and against one another in an overall assessment, always looking to conclude what was reasonable to expect of the defendant in the circumstances.