In many negligence claims the existence of a duty of care is not in issue - it is well established that certain relationships give rise to a duty, for example doctor/patient, employer/employee or driver/pedestrian. In other cases the court may have to determine whether a relevant duty existed from first principles. Last year I posted on a case in which I was involved which concerned a catastrophic injury to the driver of a motorised go-kart. She brought a claim against, amongst others, the owner of the kart. They had been two of a group of friends who had gone out karting at an empty car park on a Sunday afternoon. It was a social setting. No money exchanged hands. The claimant had been free to choose whether to drive the kart or not. Mrs Justice Swift found that no duty of care was owed.
In Yates-v-National Trust  EWHC 222 (QB) Mr Justice Nicol, as did Mrs Justice Swift, considered Caparo-v-Dickman and Tomlinson-v-Congleton  UKHL 47. in order to determine whether a duty of care was owed by the defendant to the claimant. The claim concerned an accident at Morden Hall Park, Surrey, an estate owned by the National Trust. Following a visual tree assessment the warden of the estate engaged an arborist claled Jackson to fell a diseased Horse Chestnut Tree close to Morden Lodge. Mr Jackson arrived with a team, including the claimant, to do the job. The claimant had been working from the tree for about 1 to 1.5 hours and was 50 ft from the ground when he fell.
The Judge noted that it was not contended that the NT owed to the claimant a duty to ensure that the claimant was covered by adequate insurance (although, as was noted, in some cases the absence of employers' liability insurance might be evidence of incompetence - Gwilliam-v-West Hertfordshire Hospital NHS Trust  EWCA (Civ) 1041. In some cases the He had found that the NT did not owe to the claimant a duty of care to ensure that it had chosen a competent or reputable arborist (Mr Jackson). It would not be fair and reasonable to impose on the NT a duty to the claimant to ensure that his own "boss" was competent.
"It is right that a failure to exercise reasonable care in the choice of an independent contractor might lead the NT being liable to an ordinary visitor since it could not then rely on s.2(4)(b) of the Occupiers Liability Act 1957 but it would place a very much more onerous obligation on occupiers to extend that duty to the contractor's employees or sub-contractors. That is because, as the present case illustrates, there is very much more scope for an employee to be injured than for an ordinary visitor. Therefore the range of matters which the occupier would have to take into account in order to discharge that wider duty would be considerably greater and the imposition of such a duty would not, in my view, be fair or reasonable." 
A further question arose as to whether the NT owed a duty directly to the claimant to supervise him in the conduct of his work. The Judge dismissed that proposition relying on an extract from the judgment of Lord Keith in Ferguson-v-Welsh  1WLR 1553:
"It would not ordinarily be reasonable to expect an occupier of premises having engaged a contractor whom he has reasonable grounds for regarding as competent, to supervise the contractor's activities in order to ensure that he was discharging his duty to his employees to observe a safe system of work. In special circumstances, on the other hand, where the occupier knows or has reason to suspect that the contractor is using an unsafe system of work, it might well be reasonable for the occupier to see that the system was made safe. The crux of the present case, therefore, is whether the council knew or had reason to suspect that Mr Spence, in contravention of the terms of his contract was bringing in cowboy operators who would proceed to demolish the building in thoroughly unsafe way."
Pushing the boundaries of the tort of negligence is a strenuous task.