D was doing work to the front of a house, next door to one occupied by X, blocking the main entrance to X’s house, so that they only left a dangerous alternative route. P, a visitor, was injured while using this dangerous alternative route, and HL allowed her claim of negligence against D (minus contributory negligence since she had declined help on the route).
Lord Somervell: owed a duty to all who might be expected lawfully to visit the house to take reasonable care to ensure that they were not exposed to danger. Where P was aware of the danger but, in all the circumstances, a reasonable person would have risked incurring it, the contractors were not absolved from liability either by giving a warning or by reliance on the respondent's knowledge. In considering what a reasonable person would realize or would do in a particular situation, “reasonable” does not necessarily equal what the majority of people would have done.
Lord Cohen (others agree): It is irrelevant that D would not have had a right to put up warnings/fencing along the dangerous route in X’s property since it was they who caused the initial danger by blocking the main entrance.