The case concerned both liability at common law and, importantly, breach of statutory duty relating to s. 29 (1) Factories Act 1961. This section is of great importance in asbestos litigation due to the long time is takes for diseases to develop.
The Court of Appeal had caused consternation by surprise by suggesting that one could decide retrospectively what was safe. One commentator referred to the court using a retrospectoscope.
The Supreme Court followed the orthodox line. Lord Mance said,
62. The third issue is whether the requirements regarding safety in section 29(1) are absolute or relative. In the claimant’s submission, they are absolute: what is safe is objective, unchanging and independent of any foresight of injury; the only qualification on an employer’s liability, where a workplace is unsafe because of employees’ exposure to noise, is if the employer can show that it was not reasonably practicable to reduce or avoid the exposure, e.g. by providing ear protectors. The House of Lords, by a majority, held in Nimmo v Alexander Cowan & Sons Ltd  AC 107 that the onus lies on the employer to plead and prove under section 29(1) that it was not reasonably practicable to make and keep a place safe.
63. Smith LJ  EWCA Civ 499 accepted the submission that safety is an absolute. She said that “what is objectively unsafe cannot change with time”: see para 78. She also associated lack of safety with the occurrence of injury to a single person, for she continued:
“If 85dB(A)lepd causes deafness to a particular claimant, that claimant’s place of work was not safe for him or her. It might have been safe for another person working alongside. But for the susceptible worker who has in fact been damaged, it can be demonstrated, without more, that his or her place of work was not safe. Looking at matters from the point of view of the workforce generally, it is known that a minority of people will suffer appreciable harm as the result of prolonged exposure to 85dB(A)lepd. Therefore, it can be said that the place of work is not safe for the workforce because there is a risk of injury to all of them.”
Lord Mance was not prepared to accept this.
64. I do not accept this approach. Whether a place is safe involves a judgment, one which is objectively assessed of course, but by reference to the knowledge and standards of the time. There is no such thing as an unchanging concept of safety. The Court of Appeal’s approach means in reality that any court determining an issue of safety would be applying (retrospectively) whatever happened to be the view of safety current at the time the matter came before it. Further, the fact that a single person has suffered injury due to some feature of the workplace is not, without more, proof that the workplace was unsafe. As Lord Upjohn (one of the majority) said in the Nimmo case  AC 107 , 126 c – d :
“the section requires the occupier to make [the workplace] 100 per cent safe (judged of course by a reasonable standard of care) if that is reasonably practicable and, if it is not, to make it as safe so far as is reasonably practicable to a lower percentage.”
65. Prior to the 1959 and 1961 Acts, the requirement, under regulation 5 of the Building (Safety, Health and Welfare) Regulations 1948 (SI 1948/1145), that “sufficient safe means of access shall so far as is reasonably practicable be provided” had been considered in Sheppey v Matthew T Shaw & Co Ltd  1 TLR 1272 and Trott v WE Smith (Erectors) Ltd  1 WLR 1154 (Court of Appeal). There it was said, by respectively Parker J, at p 1274, and Jenkins LJ, at p 1159, that safe cannot mean “absolutely safe”, although it must take account of circumstances likely to occur, including the fact that employees do not always behave with reasonable care for their own safety.
I also note that in the Trott case, Jenkins LJ, after suggesting that the statutory obligation was stricter than the general duty of reasonable care at common law and anticipating the Nimmo case by identifying the qualification “so far as is reasonably practicable” as involving a shift of the burden of proof (pp 1158–1159), ended his judgment by saying that to regard the standard of care prescribed by regulation 5 and at common law as approximating to each other was “if not absolutely right … at all events not very far wrong”: see p 1162.
Likewise, in…Paramor v Dover Harbour Board  2 Lloyd’s Rep 107 “that if the bare possibility of injury and accident could reasonably be foreseen, then the means of access is not ‘safe’”. In response, Salmon LJ said, at p 109, that there “is, of course, a risk of injury and accident inherent in every human operation” but that whether a means of access was safe involved “assessing the risk in all the circumstances of the case” and “must be a question of fact and degree in each case”.
66. The successor legislation to the 1961 Act, the Health and Safety at Work Act etc 1974 , was differently, and on its face more broadly, formulated. It required every employer by section 2(1) to ensure, so far as is reasonably practicable, the health, safety and welfare of all his employees, and by section 3(1) to conduct his undertaking in such a way that other persons were not thereby exposed to risks to their health or safety.
The concept of safety was considered in this context in R v Chargot Ltd… 1 WLR 1 . Lord Hope of Craighead, with whose speech all other members of the House agreed, said that the legislation was “not contemplating risks that are trivial or fanciful”, that the statutory framework was “intended to be a constructive one, not excessively burdensome”, that the law “does not aim to create an environment that is entirely risk free” and that the word “risk” which the statute uses “is directed at situations where there is a material risk to health and safety, which any reasonable person would appreciate and take steps to guard against”: see para 27.
67. It would be strange if the earlier, narrower formulation in section 29(1) had a more stringent effect. Similar comments to Lord Hope’s had also been made in the earlier case of R (Junttan Oy) v Bristol Magistrates’ Court  ICR 1475 , in relation to regulations requiring machinery to be in fact safe, “safe” being defined to mean giving rise to “no risk (apart from one reduced to a minimum) of its endangering the health of or of its being the cause or occasion of death or injury to persons”. Lord Nicholls of Birkenhead and Lord Hobhouse of Woodborough (both dissenting on presently immaterial points) made clear in that context that “safe” is not an absolute standard. Lord Nicholls said, at para 22:“There may be differences of view on whether the degree of safety of a particular piece of machinery is acceptable.”
Lord Hobhouse said, at para 103:
“to describe questions of safety as simple questions of fact, just as if one was asking whether a given bird is a sparrow or a sparrowhawk, is to make a fundamental and elementary mistake. Safety is a question of opinion. There is no such thing as absolute safety. All safety is relative. Two men can legitimately hold different opinions [as to] whether a machine is safe or unsafe. Different assessments can be and are made of the safety of a particular machine by the authorities in different countries.”
68. If safety is a relative concept, then foreseeability must play a part in determining whether a place is or was safe. Mr Hendy submits that foresight has no such role; it can come in, if at all, only at the second stage, when considering whether it was reasonably practicable to make and keep the place safe. He also notes that there was in any event, on the judge’s findings, foresight in the present case of some statistical risk of injury.
On the role of foresight, there are differing strands of authority. Not long before the 1959 Act, the House had in John Summers & Sons Ltd v Frost  AC 740 considered the requirement under section 14(1) of the 1937 Act that
“Every dangerous part of any machinery … shall be securely fenced unless it is in such a position or of such construction as to be as safe to every person employed or working on the premises as it would be if securely fenced”
and had applied to the concept of dangerousness an approach dating back to Hindle v Birtwistle  1 QB 192 , namely that a machine or part is dangerous “if in the ordinary course of human affairs danger may be reasonably anticipated from the use of them without protection”, and that it was “impossible to say that because an accident had happened once therefore the machinery was dangerous”. Lord Reid and Lord Keith of Avonholm, at pp 765–766 and 774, expressly endorsed the relevance of determining whether the degree of danger was such that there was “a reasonably foreseeable cause of injury”.
69. The same approach, again based on Hindle v Birtwistle , was followed under section 14 in Close v Steel Co of Wales Ltd  AC 367 . The claim there failed because “in the ordinary course of human affairs danger could not reasonably be anticipated from the use of the drill unfenced” (p 382, per Lord Denning, with whom Lord Morton of Henryton agreed on this point, at p 398); “the risk of injury, serious and regrettable as it proved to be, was not reasonably foreseeable” (p 389, per Lord Goddard); and “No reasonable employer could have been expected to anticipate any risk of significant injury” (p 412, per Lord Guest).
71. The concept of foreseeability continued to be adopted by courts, most notably, in Taylor v Coalite Oils & Chemicals Ltd (1967) 3 KIR 315… In the Taylor case, Diplock LJ said, obiter, at pp 319–320:
“’Safe’ is the converse of ‘dangerous’. A working place is ‘safe’ if there is nothing there which might be a reasonably foreseeable cause of injury to anyone working there, acting in a way in which a human being may reasonably be expected to act, in circumstances which may reasonably be expected to occur…In determining, therefore, whether the occupier was under a duty to take any measures to prevent an accident which was caused by the presence at a working place of a particular object, it is necessary to ask, first, whether the possibility of an object of that kind being at that particular place was reasonably foreseeable, and, if so, secondly, whether it was reasonably foreseeable that it would be a cause of injury to a person working there. It is only if both those questions are answered affirmatively that it becomes necessary to consider whether it was ‘reasonably practicable’ to avert the danger.”
72. More recently, in Robb v Salamis (M & I) Ltd  ICR 175 , Lord Hope confirmed the relevance of reasonable foreseeability to article 5(1) of the Framework Directive 89/391/EEC (imposing on employers the duty to ensure the safety and health of workers in every aspect related to the work ( OJ 1989 L275 , p 42)) and article 3(1) of the Work Equipment Directive 89/655/EEC (requiring employers to take the measures necessary to ensure that the work equipment made available to workers is suitable for the work to be carried out ( OJ 1989 L393 , p 13)), stating, at para 24: “The obligation is to anticipate situations which may give rise to accidents.”
Lord Mance then dealt with three authorities (Robertson , Larner and Mains) which appeared to point in a different direction. He concluded,
76. In so far as the Robertson, Larner and Mains cases stand for a proposition accepted by the Court of Appeal in the present case, that safety is an eternal absolute independent of any judgment based on current standards and attitudes, then I do not accept their correctness.
One factor in the decisions in both the Larner and Robertson cases was that the introduction of foreseeability would reduce the “utility of the section”, by frequently limiting success under it to circumstances in which a common law claim for negligence would succeed ( Larner , p 560 a , per Hirst LJ, and p 562 c – d , per Peter Gibson J; Mains , p 531 d – e , per Lord Sutherland, and pp 535 g – h and 536 h -537 b , per Lord Johnston). This begs the question as to the intended scope and effect of the section. Not only does the section introduce criminal sanctions, but, as established in the Nimmo case, if the workplace is unsafe, then the burden shifts to the employer to show that it was not reasonably practicable to make and keep it safe. It was in this connection that in Nimmo… (at) 122 f – g , Lord Guest said that he could “not think that the section was intended to place such a limited obligation on employers” as they would have at common law (where it would be for an injured employee to plead and prove failure to take reasonably practicable steps) and that Lord Upjohn (whose view that safety is “judged of course by a reasonable standard” I have already quoted in para 64 above) added, at p 125 b , that “it is not in doubt that the whole object of the Factories Act is to reinforce the common law obligation of the employer to take care for the safety of his workmen”.
77. Further, section 29(1) imposes a non-delegable duty, so that an employer is responsible for achieving or for the taking all reasonably practicable measures to achieve the requisite safety irrespective of whether he chooses to set about doing this through himself, his servants or independent contractors.
78. There is nothing to show that section 29(1) was intended to go further, and there is no assumption (or, in my opinion, likelihood) that it was intended to. The standard of reasonableness expressed in the qualification “so far as is reasonably practicable” (in respect of which the onus of proof is on the employer) makes it more, rather than less, likely in my view that the concept of safety is itself to be judged, as Lord Upjohn thought obvious in the Nimmo case, by reference to what would, according to the knowledge and standards of the relevant time, have been regarded as safe…
80. In summary, safety must, in my view, be judged according to the general knowledge and standards of the times. The onus is on the employee to show that the workplace was unsafe in this basic sense.
Italics added. Edited for ease of reading.