Blyth v Birmingham Waterworks Co.

• The defendant water company had installed a water main fitted with a fire plug, constructed according to the best standards known at the time. An extraordinarily severe frost, of unprecedented severity, caused the plug to fail, resulting in water damage to the plaintiff's property. The plaintiff sued in negligence.

1. What standard governs whether a defendant's conduct constitutes negligence.

• The court formulated negligence as the omission to do something a reasonable person, guided by ordinary considerations governing human conduct, would do, or doing something a prudent, reasonable person would not do. Since the defendant's works were constructed to the best known standards, and the frost's severity was unprecedented and not reasonably foreseeable, no negligence was established.

Negligence is assessed against an objective standard: what a reasonable, prudent person would or would not do in the circumstances. A defendant meeting this standard is not negligent merely because an extraordinary, unforeseeable event causes harm.