“Tort is what is in the tort books, and the only thing holding it together is their binding... Naturally there are horses for courses, and the tort course sports quite a lot of horses, of very different breeds and speeds” (Weir, An Introduction to Tort Law (2006), p. ix). Despite several academic efforts to explain when non-delegable duties arise and their theoretical relationship with vicarious liability, the conceptual underpinnings of this area of tort law remain contentious: the horses of vicarious liability and non-delegable duties continue to run uneasily alongside each other. Nonetheless, some doctrinal boundaries are not difficult to draw in a crude form, especially as regards negligence. Under vicarious liability, an employer is liable to a third party if the tort is committed by his employee in the course of his employment. If the tortfeasor is not his employee but an independent contractor, the employer is not liable for the latter's negligence unless he owes the third party a non-delegable duty.

Certain aspects of this area have recently been revisited in Biffa Waste Services Ltd. v. Maschinenfabrik Ernst Hese GmbH and others [2008] EWCA Civ 1257; [2009] Q.B. 725. The dispute arose from a fire caused at a recycling plant under construction. Biffa Waste engaged Maschinenfabrik Ernst Hese (“M”) to design and build the plant and M sub-contracted the work to Hese Umwelt (“H”). In turn, H entered into a contract with Outokumpu Wenmec (“OT”) to supply and install the “ball mill,” an integral part of the plant. OT arranged for sub-contractors Pickfords (“P”) to carry out necessary welding work to the “ball mill.” The fire occurred during the welding work as a result of P's negligence. With P and H insolvent, Biffa Waste sought compensation from M in contract and tort and from OT in tort. The latter claim, which formed the subject-matter of the current appeal, was based on two grounds, both of which were rejected by the Court of Appeal.

First, Biffa Waste asserted that because OT had undertaken to supervise P's work, P became their “borrowed employee,” making OT vicariously liable for P's negligence. The trial judge agreed, but his decision was reversed on appeal. Whilst he was right, in line with the leading case of Mersey Docks and Harbour Board v. Coggins & Griffith (Liverpool) Ltd. [1947] A.C. 1, to rely on “control” as the test for determining the welders' employer, he erred in equating supervision with control: “The right to supervise does not, without more, carry with it the entitlement to instruct how to do the work, particularly where the employees are not unskilled labourers but skilled welders” (at [56]). In this context, the relevant “control” is that exercised vis-à-vis the manner of execution of the particular work, with the focus of the enquiry being on the negligent act (at [51]). Given that the welders provided by P were skilled, used their own equipment and were also supervised by their own foreman, OT did not have the requisite control over them. Additionally, the welders were not OT's employees because they were not integrated into OT's business undertaking as their work lasted only for one weekend and was therefore temporary (at [55]). By examining both “control” (per May L.J. in Viasystems Ltd. v. Thermal Transfer [2005] EWCA Civ 1151) and “integration” (per Rix L.J. in Viasystems), the Court of Appeal avoided a choice between the two approaches. This might be seen as a missed opportunity to settle the doctrinal basis of vicarious liability in cases of “borrowed employees,” especially since the different approaches might serve different policy considerations (on this, see Stevens (2006) 122 L.Q.R. 201, 204). However, it reflects the recent tendency of the courts to take a more flexible and composite approach when determining the existence of an employer/employee relationship in vicarious liability cases, thereby considering multiple and often case-specific factors. Finally, the Court of Appeal reiterated that “the burden on a party seeking to show a transfer or assumption of liability to or by the hirer of an employee is a heavy one” (at [59]). This makes it necessary to establish “exceptional facts” before a contractor is vicariously liable for his sub-contractor's negligence and ensures that in most cases it is the employer with most information that bears the risk on account of being the best placed to monitor the employee.

Biffa Waste's second ground was based on the decision of the Court of Appeal in Honeywill & Stein Ltd. v. Larkin Bros. [1934] 1 K.B. 191, from which the trial judge derived the principle that “a person who employs an independent contractor will be liable for the negligence of that independent contractor where the independent contractor is engaged to carry out ‘extra-hazardous or dangerous operations’ … The employer is under a non-delegable duty to see that all reasonable precautions are observed, otherwise he will be responsible for the consequences” (at [63]). Finding against Biffa Waste and reversing the trial judge's decision, the Court of Appeal held that the activity in question was not extra-hazardous. The activity to be judged was welding per se, not welding in the vicinity of unwetted combustible material (at [81]). Furthermore, despite Slesser L.J.'s contrary remarks in Honeywill, it was irrational to exclude available precautionary measures when assessing the activity's dangerousness (at [75]). Thus OT should not have been held liable for the damage caused by the welding having been carried out without the taking of the proper precautions.

More broadly, the Court of Appeal expressed support for the criticism of Honeywill, which has centred on the imprecise meaning of “extra-hazardous” (e.g. Atiyah, Vicarious Liability in the Law of Torts (1967), p. 371). In a previous decision of the same court (Bottomley v. Todmorden Cricket Club [2003] EWCA Civ 1575), Brooke L.J. applauded the rejection of the doctrine in Australia (Stevens v. Brodribb Sawmilling Company Pty. Ltd. [1986] HCA 1) and hoped that the Supreme Court would follow the same path. Echoing similar feelings, the Court of Appeal in Biffa Waste stated that the Honeywill doctrine “is so unsatisfactory that its application should be kept as narrow as possible. It should be applied only to activities that are exceptionally dangerous whatever precautions are taken” (at [78]). In its current form, the doctrine of non-delegable duty for extra-hazardous activities is down but not out. Whilst it is nearly impossible to present a concise definition of “extra-hazardous,” one way of getting round this might be to provide a list of relevant factors, like, for example, §520 of the US Restatement (Second) of Torts. But this, like Honeywill, would be out of step with the House of Lords' denunciation of the distinction between activities that are obviously dangerous and those that are not on the basis that it is impractical and unsound, in Read v. J Lyons & Co. Ltd. [1947] A.C. 156 (whilst rejecting a tort of strict liability for extra-hazardous acts). A more realistic option, therefore, might be to do away with the doctrine and concentrate instead on the degree of care which an employer must exercise in such cases. If he engages an independent contractor to carry out an activity with a high risk of serious damage, then he should be placed under a correspondingly high standard of care to ensure that the independent contractor is careful. This, of course, would not sort out the muddle that surrounds the area of non-delegable duties, but it would, at least, remove one of its ingredients.