If successful, the 49-year-old teacher stands to win at least #163;50,000 in damages from his employer - and encourage other burnt-out teachers to make similar claims. But the National Association of Schoolmasters Union of Women Teachers, which has taken up his case and will have to pay both sides’ legal costs if he loses, does not anticipate a flood of cases reaching the courts.

While proposed changes to the Teachers’ Superannuation Scheme which will make it harder for stressed teachers to take early retirement could well fuel interest in litigation, it is technically very difficult to win damages for health problems brought on by stress at work.

Describing the whole area of stress claims as “job creation for lawyers”, NASUWT legal officer Jerry Bartlett says: “There are many cases in which we are absolutely convinced that there has been unacceptable management conduct constituting bullying in the worst cases, but applying the standards of proof required by the courts is extremely difficult.

“There is also an enormous problem with expert medical evidence in that whilst it is not difficult to secure a diagnosis that a person is suffering from stress-related illness, securing a medical opinion as to the causes of that stress is much more difficult.”

As well as proving that stressful working conditions or excessive workloads caused their health problems, claimants have to show that their employers knew their health was at risk.

Getting over all these technical obst-acles is not easy, which is why after asking solicitors to look into 53 potential compensation claims this year, the NASUWT has come close to starting legal proceedings in just eight cases. Several of these have now collapsed, leaving only one case which will go to court unless a settlement is reached first.

John Usher of the Leeds law firm Thompson, the solicitor looking after this case, also acted for John Walker, the Northumberland social worker who in 1994 became the first person in Britain to successfully sue his employer in a stress-related case. Although no one has won a similar case since, Mr Usher says this is because the precedent established by the Walker case is fairly recent and other cases are inevitably taking a long time to reach the courts.

Predicting that increasingly overburdened teachers will be among those who win compensation for illness caused by stress at work, he adds: “I think that in percentage terms the number of cases that succeed as compared to the number of teachers will not be large, but nevertheless the costs to employers of the occasional successful case is going to be more than enough to make them take the issue more seriously.”

It is impossible to predict exactly how much compensation the courts will award in individual cases. Graham Clayton, solicitor for the National Union of Teachers, which has half-a-dozen cases in the pipeline, says claims could run to “tens of thousands” of pounds.

John Usher had to certify that he expected damages to be in excess of #163;50,000 before issuing High Court proceedings on behalf of the NASUWT member he represents. But they could be a lot more. John Walker, who was 15 years away from retirement age when he had to abandon his social work career on medical grounds, received #163;175,000.

Awards to younger applicants could be even higher. If they manage to show that their careers have ended prematurely they will be able to claim for loss of earnings up to the normal retirement age as well as the loss of opportunity to contribute to an occupational pension scheme.

The Department for Social Security’s Industrial Injury Benefit Scheme offers an alternative to litigation for teachers who are too ill to carry on working but fail to satisfy the stringent requirements laid down in the Walker case. This non-means-tested scheme is designed to compensate people who have suffered industrial injury, and does not require applicants to show that their employers have been at fault. Payments are worth between #163;19.06 and #163;95.30 a week, depending on the degree of disability of the applicant.

However, only one teacher - again an NASUWT member - has so far managed to persuade DSS adjudication officers that a stress-related illness constituted an industrial injury. That teacher now receives a weekly industrial injuries disablement benefit. But other teachers who have tried to build on this precedent have found adjudicators unsympathetic.

The Disability Discrimination Act, which comes into force this month, offers more hope to teachers who become seriously ill - whether as a result of stress or other factors. Under this Act employers are obliged to make appropriate provision for disabled employees. The employer’s fault is not an issue: all employees have to show is that their disability has lasted or is likely to last for 12 months. The employer then has to assess their working conditions and make such reasonable adjustments as will enable them to stay in employment. Failure to do so counts as unlawful discrimination and could land the employer in front of an industrial tribunal.