Court dismisses claim based on workplace stress where there was no evidence that the employer knew of the risk

England and Wales

Employees face a high hurdle when attempting to prove that their employer is liable for stress-induced psychiatric injury, as shown in the recent case of Mackenzie v AA plc and another [2021] EWHC 1065 (QB). The reminder is timely. There is preliminary evidence that a significant proportion of those who become ill with COVID-19 go on to develop mental health issues. Furthermore, the pandemic has created a stressful working environment for many, including the prospect of redundancy for some as the furlough scheme is wound down. The ingredients for a spike in workplace stress claims are there but proving the essential elements will continue to be a challenge for claimants.


The claimant, formerly Executive Chairman and CEO of AA plc, was summarily dismissed by AA plc on 1 August 2017 for gross misconduct. He had assaulted a colleague after drinking heavily at a strategy away day on 24 July 2017.

The claimant sued AA plc, alleging that his behaviour was as a consequence of psychiatric illness caused by stress at work. He argued that the board and senior management were aware that he had become overstressed as a consequence of his considerable workload and that this had caused a deterioration in his physical and mental health, culminating in the development of severe generalised anxiety disorder and depression. He alleged that the assault and his subsequent dismissal were caused by the defendant’s failure to take reasonable care for his health and safety.

The decision

The defendant applied for summary judgment on the basis that the claimant’s personal injury claim had no realistic prospect of success. The court agreed. It was found that the claimant was unable to provide any evidence that the defendant knew or ought to have known that, as a result of stress at work, there was a risk he would develop a psychiatric injury. Indeed, his own expert evidence tended to support the conclusion that they could not have foreseen such an injury.

The requirements for summary judgment (no real prospect of success and no other compelling reason why the issue should be disposed of at trial) were satisfied, and the personal injury claim was dismissed.

In reaching this conclusion, the judge summarised the key principles applicable to workplace stress claims. In particular, the psychiatric injury must have been foreseeable by the defendant, which in this case, it was not. When considering foreseeability, the judgment set out some established principles which bear repeating:

  • It is not enough to show that the defendant knew the claimant had too much work to do, or even that they were vulnerable to stress as a result of overwork. Mere stress is not enough. It must be shown that the defendant knew or ought to have known that, as a result of stress at work, there was a real risk of injury;
  • An employer is entitled to assume that an employee can withstand the normal pressures of the job, in the absence of clear evidence to the contrary (for example, other employees having become ill doing the same work, or where the employer knows or ought to know that the employee in question is especially vulnerable to stress- induced illness);
  • An employer only has a duty to act when the indications of imminent harm are plain enough for any reasonable employer to realise it should do so;
  • An employer has no general obligation to make searching or intrusive enquiries and may take at face-value what an employee tells it.


The mental health and wellbeing of employees has been much discussed during the pandemic, and there is an increasing recognition that “working from home” can be a source of considerable stress to some. However, although the pandemic, its associated illness and the profound changes to the working environment in response have undoubtedly placed considerable strain on many employees, claims for stress-related psychiatric injury will remain challenging for claimants and should be subject to very careful scrutiny by defendants.

Defending workplace stress claims can be extremely time-consuming and costly. Where, as here, it becomes evident that the claim fails to meet the exacting evidential standard required, an application for summary judgment may well be appropriate, terminating the claim early and saving further legal expenditure.