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Why Mansfield v Weetabix Ltd is important

In Mansfield v Weetabix, the Court of Appeal overturned the approach in Roberts v Ramsbottom. In that case, the Court required a ‘total loss of consciousness’, or actions which were ‘wholly beyond [the defendant’s] control’. Instead, Mansfield v Weetabix the Court asked whether, objectively, the claimant failed to take reasonable care.


A lorry owned by Weetabix Ltd failed to take a sharp bend and crashed into the claimants’ shop. The driver, Mr Tarleton, unknowingly suffered from malignant insulinoma. This condition starved his brain of glucose, meaning his brain did not function properly. This was why he failed to take the turn and crashed into the Mansfields’ shop. Nevertheless, it was shown that Mr Tarleton did brake just before crashing into the shop, meaning he did retain some degree of consciousness.

In the 40 miles prior to crashing into the Mansfields’ shop, Mr Tarleton was also involved in three other incidents: he drove erratically on a dual carriageway, collided with a trailer pulled by the vehicle in front of him, and at one point unexpectedly mounted the kerb.


The Mansfields brought a claim in the tort of negligence against Weetabix Ltd, arguing they were vicariously liable for Mr Tarleton’s alleged negligence. The case reached the Court of Appeal.


The issue for the Court of Appeal was whether Mr Tarleton had failed to take reasonable care. The judge found that the claimant had not had much to eat that day, and therefore held he was negligence. The Judge followed the Court’s ruling in Roberts v Ramsbottom, concluding that the defendant had retained some degree of consciousness and was therefore negligent.

The defendants contested that Mr Tarleton was negligent, arguing that he was unable to appreciate his inability to drive and could not, therefore, be said to have failed to take reasonable care.


The Court of Appeal overturned the Judge’s ruling, concluding that Mr Tarleton had not failed to take reasonable care.


The leading judgement was given by Leggatt LJ.

Leggatt LJ rejected Neil J’s comparison with the criminal law in Roberts v Ramsbottom. In the criminal law, the question is whether the defendant was ‘driving’, and hence it is important to show a state of ‘automatism’. However, this is not the test for negligence, nor should be. Leggatt LJ rejected that any other test would lead to uncertainty in the law.

Instead, Leggatt LJ asked himself whether Mr Tarleton had showed the standard expected of a man suffering from this rare and unknown condition. It was important that Mr Tarleton was not aware (nor ought to have been aware) that he was unfit to drive. Therefore, Leggatt LJ held he had not failed to take reasonable care. In the words of Leggatt LJ:

In my judgment, the standard of care that Mr. Tarleton was obliged to show in these circumstances was that which is to be expected of a reasonably competent driver unaware that he is or may be suffering from a condition that impairs his ability to drive. To apply an objective standard in a way that did not take account of Mr. Tarleton’s condition would be to impose strict liability

Leggatt LJ nevertheless concluded that Roberts v Ramsbottom was rightly decided on the alternative ground that the defendant continued to drive when he was both unfit to do so and aware he was unfit to do so.

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