Introduction
The rule in Rylands v Fletcher establishes a form of strict liability for harm caused by the escape of dangerous things from a person's land. Originating in the nineteenth century, it provides a cause of action in tort that sits between private nuisance and negligence. For a claimant to succeed, several key ingredients must be proven. As established in the definitive judgment of Blackburn J, these are: the defendant brings something onto their land for their own purposes; the thing is likely to do mischief if it escapes; there is a non-natural use of the land; the thing does escape and causes foreseeable damage (Horsey and Rackley, 2021). This essay will focus on the second of these ingredients: the requirement that the defendant has collected a ‘thing likely to do mischief if it escapes’. This essay will explain how this element has been interpreted by the courts. It will be shown that the test is not concerned with things that are inherently dangerous, but rather with things that pose a foreseeable risk of harm upon escaping. Furthermore, the analysis will demonstrate that the modern interpretation of this requirement, particularly following the House of Lords' decision in Transco plc v Stockport MBC, has significantly narrowed its scope by connecting it to notions of extraordinary risk.
The Original Formulation: ‘Likely to do Mischief if it Escapes’
The classic formulation of the rule was provided by Blackburn J in the Court of Exchequer Chamber in Rylands v Fletcher (1866). He stated that:
> ‘the person who for his own purposes brings on his lands and collects and keeps there anything likely to do mischief if it escapes, must keep it in at his peril, and, if he does not do so, is prima facie answerable for all the damage which is the natural consequence of its escape’ (Rylands v Fletcher (1866), at 279).
In the case itself, the ‘thing’ was a large quantity of water that the defendants had accumulated in a new reservoir. The water escaped through disused mine shafts and flooded the claimant’s neighbouring mine. Critically, water itself is not inherently dangerous. The key to understanding Blackburn J's principle lies in the phrase ‘if it escapes’. The principle is concerned with the potential for harm should the accumulated thing be released from the defendant's control. The potential for ‘mischief’ arose from the fact that a huge volume of water, if it escaped, would inevitably cause damage by its very nature. Therefore, the focus is on the foreseeability of harm resulting from an escape, not the intrinsic danger of the substance itself.
This interpretation was applied in early cases to a variety of situations. For instance, in Musgrove v Pandelis (1919), the court held that a car in a garage with a full tank of petrol was a thing ‘likely to do mischief if it escapes’. At that time, motor cars were relatively new, and the storage of petrol was seen as creating a special danger. Again, petrol is not dangerous when contained, but if it were to escape and ignite, the potential for destructive fire was high. Similarly, electricity (National Telephone Co v Baker (1893)), explosive materials (Rainham Chemical Works Ltd v Belvedere Fish Guano Co Ltd (1921)), and noxious fumes (Halsey v Esso Petroleum Co Ltd (1961)) have all been held to satisfy this requirement. These cases illustrate that the courts have been prepared to apply the rule to a wide range of substances and items, provided their escape would foreseeably cause damage.
The Relationship with ‘Non-Natural Use’
The ingredient of a ‘thing likely to do mischief’ cannot be understood in isolation. It is closely connected to the separate requirement that the defendant’s activity must constitute a ‘non-natural use’ of the land. This second concept was added by Lord Cairns in the House of Lords appeal of Rylands v Fletcher (1868) and has been central to the tort's development. Lord Moulton, in Rickards v Lothian (1913), provided a classic definition of non-natural use as a "special use bringing with it increased danger to others," as opposed to "the ordinary use of the land or such a use as is proper for the general benefit of the community" (Rickards v Lothian (1913), at 280).
The two elements often overlap and inform one another. The accumulation of something that brings an "increased danger" is often the very same thing that is "likely to do mischief if it escapes". For example, in Cambridge Water Co v Eastern Counties Leather plc (1994), the storage of industrial solvents in substantial quantities on a factory site was considered a classic example of non-natural use. Equally, the solvents (PCEs) were clearly things likely to do mischief if they escaped by seeping into the ground and contaminating the water table. The decision to classify a use as 'non-natural' is often influenced by the dangerous potential of the thing being accumulated.
However, some commentators and judges have questioned whether there is a meaningful distinction between the two elements. For example, Viscount Simon in Read v J Lyons & Co Ltd (1947) suggested that for the rule to apply, the thing brought onto the land must be "dangerous in itself". This would mean that the 'dangerous thing' and 'non-natural use' tests were effectively asking the same question. This view, however, has not been widely adopted. The orthodox position remains that Blackburn J’s test is distinct: the thing need not be dangerous in itself, but it must be something that poses a risk of harm upon escape. The accumulation of a very large quantity of a normally harmless substance, like water in Rylands, can satisfy the test.
The Modern Approach: Foreseeability and ‘Exceptionally High Risk’
The modern scope of Rylands v Fletcher has been substantially clarified and constrained by two key House of Lords decisions. The first, Cambridge Water, established that the damage caused by the escape must be of a type that was reasonably foreseeable to the defendant. Lord Goff confirmed that foreseeability of harm is an essential prerequisite for liability, aligning the rule more closely with nuisance and negligence in this respect. This means that for the ‘mischief’ element to be satisfied, the defendant must have been able to foresee the type of damage that would occur if the accumulated thing escaped.
The second, and most definitive, modern authority is Transco plc v Stockport MBC (2004). In this case, a large water pipe supplying a block of flats failed, releasing a significant volume of water which washed away an embankment supporting the claimant’s high-pressure gas main. The House of Lords held that the rule in Rylands v Fletcher did not apply. In his leading judgment, Lord Bingham restated the requirements for the tort. On the issue of the dangerous thing, he formulated the test in a much stricter manner. He stated that the rule is engaged only where:
> ‘the defendant has done something which he recognised, or judged by the standards appropriate at the relevant place and time, he ought to have recognised, as giving rise to an exceptionally high risk of danger or mischief if there should be an escape’ (Transco plc v Stockport MBC (2004), at para 10).
This use of the phrase ‘exceptionally high risk’ is significant. It suggests that a mere foreseeable risk of some mischief is no longer sufficient. Liability will only be imposed for the accumulation of things that create a danger that is out of the ordinary. In Transco, the piping of water for domestic use to a block of flats was held to be a normal and ordinary activity that did not create an "exceptionally high risk". Lord Hoffmann, in the same case, described the objects of the rule as "creating a greater than usual risk of damage" (para 35). This modern interpretation effectively fuses the ‘mischief’ element with the ‘non-natural use’ element into a single, high-threshold question: has the defendant engaged in an activity that creates an exceptional risk?
Conclusion
In conclusion, the requirement that a defendant must accumulate a ‘thing likely to do mischief if it escapes’ has been a central component of the tort in Rylands v Fletcher since its inception. The courts have consistently held that the test is not whether the thing is inherently dangerous, but whether its escape would foreseeably cause harm. Case law demonstrates its application to a wide array of items, from water and petrol to chemicals and electricity.
However, the interpretation of this element has evolved significantly. While it was once a relatively flexible concept, the modern jurisprudence, especially the judgment of the House of Lords in Transco, has substantially raised the bar for claimants. The introduction of the ‘exceptionally high risk’ standard by Lord Bingham means that the rule is now reserved for situations that are truly out of the ordinary. This has drawn the ‘mischief’ element much closer to the test for ‘non-natural use’, to the point where they are almost inseparable. The result is that this ingredient, like the tort itself, now has a very narrow application, confined to cases where a defendant has created a risk that is clearly beyond the everyday and acceptable incidents of modern life.
References
Attorney-General v Corke [1933] Ch 89.
Cambridge Water Co v Eastern Counties Leather plc [1994] 2 AC 264.
Halsey v Esso Petroleum Co Ltd [1961] 1 WLR 683.
Horsey, K. and Rackley, E. (2021) Tort Law. 7th edn. Oxford University Press.
Musgrove v Pandelis [1919] 2 KB 43.
National Telephone Co v Baker [1893] 2 Ch 186.
Rainham Chemical Works Ltd v Belvedere Fish Guano Co Ltd [1921] 2 AC 465.
Read v J Lyons & Co Ltd [1947] AC 156.
Rickards v Lothian [1913] AC 263.
Rylands v Fletcher (1866) LR 1 Ex 265; (1868) LR 3 HL 330.
Transco plc v Stockport MBC [2004] 2 AC 1.
