Quick answer: To win a negligence claim, the claimant must prove the breach caused the damage and that the damage was not too remote. Factual causation uses the but-for test (Barnett v Chelsea & Kensington HMC). Legal causation asks whether a novus actus interveniens broke the chain. Remoteness asks whether the type of damage was reasonably foreseeable (The Wagon Mound (No 1)).
Duty and breach get most of the attention in negligence, but many problem questions are decided at the final stage: causation and remoteness of damage. This is topic 4.1.4 of Paper 4 (Law of Tort) in the Cambridge 9084 syllabus. If you need a refresher on the earlier stages, start with negligence: duty, breach and damage.
1. Factual Causation: The But-For Test
The starting question is: but for the defendant’s breach, would the claimant have suffered the damage? If the damage would have happened anyway, the breach did not cause it.
In Barnett v Chelsea & Kensington Hospital Management Committee (1969), a doctor negligently refused to examine a man who had been poisoned with arsenic. The man died, but the evidence showed he would have died even with proper treatment. The hospital was not liable because the but-for test was not met.
Problems with the but-for test
- Multiple possible causes: in Wilsher v Essex Area Health Authority (1988), excess oxygen was only one of five possible causes of a premature baby’s blindness, so the claimant could not prove causation.
- Material contribution: in Bonnington Castings v Wardlaw (1956), the defendant’s breach made a material contribution to the claimant’s lung disease, which was enough.
- Loss of a chance: in Hotson v East Berkshire AHA (1987), a claimant who had only a 25% chance of recovery anyway could not recover for the lost chance, because on the balance of probabilities the breach did not cause the harm.
2. Legal Causation: Novus Actus Interveniens
Even if the but-for test is met, the chain of causation can be broken by a new intervening act, so the defendant is not liable for the later damage.
- Act of a third party: in Knightley v Johns (1982), a police officer’s negligent order to ride the wrong way through a tunnel broke the chain from the original accident. In Lamb v Camden LBC (1981), squatters damaging an empty house was too remote from the council’s negligence.
- Act of the claimant: in McKew v Holland & Hannen & Cubitts (1969), the claimant, whose leg was weakened by the defendant’s negligence, went down a steep staircase without a handrail and fell. His own unreasonable conduct broke the chain.
- Natural events: an unforeseeable natural event can also break the chain.
Foreseeable interventions, such as a rescuer stepping in or a reasonable medical response, usually do not break the chain.
3. Remoteness of Damage
From Re Polemis to The Wagon Mound
In Re Polemis (1921), the test was whether the damage was a direct consequence of the breach. This was replaced by the Privy Council in Overseas Tankship v Morts Dock (The Wagon Mound No 1) (1961): the defendant is only liable for damage of a type that was reasonably foreseeable. Oil spilled in Sydney Harbour caught fire and destroyed a wharf; fire damage was not foreseeable because the oil was not thought likely to ignite on water, so the defendant was not liable.
Type of damage, not exact way it happened
- Hughes v Lord Advocate (1963) – boys were burned when a paraffin lamp left by workmen exploded. Burns were a foreseeable type of harm, even though the explosion itself was not; the defendant was liable.
- Doughty v Turner Manufacturing (1964) – a lid slipped into molten metal, causing an unforeseeable chemical eruption. Splashing was foreseeable, but eruption was a different kind of harm; no liability.
- Jolley v Sutton LBC (2000) – children injured while repairing an abandoned boat. The House of Lords took a broad view: it was foreseeable that children would meddle with the boat and be hurt.
The thin skull (eggshell skull) rule
If some injury is foreseeable, the defendant must take the victim as they find them and is liable for the full extent of the harm, even if it is much worse because of the claimant’s condition. In Smith v Leech Brain (1962), a burn to the lip from molten metal triggered cancer in a man with a pre-cancerous condition, and the employer was liable for his death.
Evaluation: Are the Rules Fair?
- The but-for test is simple and works for most cases, but it struggles with multiple causes and medical uncertainty, leaving some deserving claimants without compensation (Wilsher, Hotson).
- The Wagon Mound foreseeability test is fairer to defendants than Re Polemis, but the line between “type” and “extent” of harm can be arbitrary (compare Hughes and Doughty).
- The thin skull rule protects vulnerable claimants but can impose liability far beyond what the defendant could expect.
Exam Structure for Causation Questions
- Apply the but-for test to the facts.
- Consider any intervening act and whether it was foreseeable.
- Ask whether the type of damage was foreseeable (Wagon Mound, Hughes).
- Apply the thin skull rule if the claimant had a pre-existing condition.
- Consider defences and remedies, such as contributory negligence.
Practise with the free Paper 4 tort notes, and see how causation connects to psychiatric injury and vicarious liability.
Free Past Papers and Notes – Download Now
Lock this topic in by practising real Cambridge questions and revising with our free notes:
→ Download Free A Level Law Past Papers & Mark Schemes
→ Free A Level Law Notes (PDF)
→ Free A Level Law Paper 4 Notes: Law of Tort
Check where this topic sits in the official Cambridge International AS & A Level Law 9084 syllabus.
About Sir Owais Mirchawala’s A Level Law Classes
Sir Owais Mirchawala teaches Cambridge International AS & A Level Law (9084) to students across Pakistan and the Gulf. His A2 Level Law course covers Papers 3 and 4 topic by topic through recorded lectures you can study at your own pace, with topical past paper practice, class notes, WhatsApp query support, and homework and mock exam marking. Learn more about Sir Owais Mirchawala, explore the A2 Level Law course, read the A Level Law course FAQs, or message him on WhatsApp to enrol.
Frequently Asked Questions
What is the but-for test in negligence?
It asks whether the claimant would have suffered the damage but for the defendant's breach. If the damage would have happened anyway, as in Barnett v Chelsea & Kensington HMC, causation is not established.
What is novus actus interveniens?
It is a new intervening act, by a third party, the claimant or a natural event, that breaks the chain of causation so the defendant is not liable for the later damage.
What did The Wagon Mound decide?
The Wagon Mound (No 1) held that a defendant is only liable for damage of a type that was reasonably foreseeable, replacing the direct consequence test from Re Polemis.
What is the thin skull rule?
If some harm to the claimant was foreseeable, the defendant is liable for the full extent of the harm, even if it is more serious because of the claimant's pre-existing condition, as in Smith v Leech Brain.
Final Thought
Causation and remoteness turn good negligence answers into excellent ones. Work through factual causation, legal causation and remoteness in that order, support each with a leading case, and you will pick up application marks that many students miss.