Few jobs have been done by so many so briefly. Apart from occupations that are more or less obsolete (millworkers, miners), transitory (waiters, bar staff) or seasonal, no trade or profession is so frequently prefixed with the word “former” as teacher.

Part of the reason is that the UK has so many teachers to start with - the equivalent of nearly 430,000 full-time staff. And with one in three leaving the profession within five years of qualifying, you don’t need GCSE maths to see that there are many more former teachers out there. Workload and the need for new challenges are often cited as the major causes of the brain drain. But not everybody who quits the classroom is lost to the profession; a teaching qualification is a passport to all kinds of related work and there’s a well-trodden path to jobs such as teaching abroad, consultancy and inspection work or educational writing.

Celebrities who were once teachers wear their status like a badge of honour, as if the fact they used to have a proper job gives credibility to their current position. Comedians, writers, pop stars and politicians: their ranks have all been successfully infiltrated by former teachers. Yet others take off in an entirely different direction. Here we profile four former teachers who turned their talents to more unexpected occupations.

JOHN PODMORE: PRISON GOVERNOR

John Podmore spent eight years as a teacher. He enjoyed it for four years, tolerated it for two more and spent the final two planning his escape.

Ironic, then, that he should end up in prison. “I had hit the buffers in terms of promotion. I was young, I was ambitious and I was getting nowhere.”

Holed up in hospital following an operation, he spotted a newspaper advertisement. The Prison Service was looking for assistant governors. He applied and, after a gruelling three-day interview, he was in. “I took to it fairly easily. I quickly got a level of responsibility I found breathtaking.” Eighteen months after leaving his job as a teacher of everything from maths and PE to geology and economics at an East Sussex comprehensive, he was at Parkhurst prison assessing the suitability for transfer of the East End gangster Ronnie Kray.

He rose through the ranks until he was appointed governor of Brixton prison in February 2003. Given a level one ranking - the lowest possible - by prison inspectors, Brixton was officially the worst jail in the country.

Today it has a level two ranking and is one of the most improved of London’s eight prisons.

The demographics of HMPBrixton are enough to make the battle-hardened head of any inner-city school shudder. Of its 800 prisoners, 80 per cent are crack cocaine users, 70 per cent have a history of mental illness, and 50 per cent have a reading age of seven. Understandably, the priorities are somewhat different from school. “My first duty is preservation of life. We had three suicides last year and that’s hard. The last time, I was shopping and the phone rang: ‘Someone’s hanged himself.’ We save lives daily. When you look at the substance misuse, the exclusion and deprivation issues, it’s a high-risk population.”

There are similarities with school, he says. “I had skills as a teacher that are helpful in this environment. It doesn’t bother me standing up and talking to people; schools are in the people business, prisons are in the people business.”

He says his job is “far more complex and varied than teaching” but sometimes it reminds him of his previous employment. “I have had many a confrontation with a murderer or armed robber and reflected on similar run-ins with aggressive 14 or 15-year-olds who didn’t want to be at school.”

Despite working in an institution that was condemned in 1842, and where the cells are “the size of two toilet cubicles”, Mr Podmore has a vision of Brixton as a community prison. He lives locally and says nothing gives him more pleasure than meeting a former prisoner whose life has improved. “I used to get more aggravation from ex-pupils than I do from ex-prisoners,” he says.

From an annual budget of pound;20 million, pound;500,000 is earmarked for education. Given that many prisoners are on remand or serving short sentences, there’s only so much he can do, and so much else that needs doing. But the Dream Factory, a performance project begun last year, staged a hugely successful show for prisoners and visitors, and two of the cast have since found work as actors. “There are more downs than ups in this job,” says Mr Podmore. “I am still passionate about education.”

LOUISE MULCAHY: MIDWIFE

Louise Mulcahy’s life changed on February 20, 1998, the day she gave birth to Sophie. It wasn’t so much the arrival of a child that was so dramatic - she was already a mother to Emily and Harriet - but the manner of her third child’s arrival. Sophie was born 11 weeks premature. “It was traumatic,” says Ms Mulcahy. “You don’t expect things to go wrong. You think you will go to term and deliver a nice, healthy baby. Her skin was bright red, translucent; she looked like a skinned rabbit. She was so small I could cover her head with my hand.”

For weeks afterwards, Sophie stayed in the special care baby unit of Kingston hospital, Surrey. Slowly, she got stronger. Now, aged nearly seven, she is the tallest in her class. For Ms Mulcahy, who had been working part-time as a geography teacher at Danes Hill school in Oxshott, Surrey, since the birth of her second child, the experience was “the trigger” for her to think about leaving the classroom to retrain as a midwife. She had helped a friend cope with the trauma of a stillbirth and thought: “If I can do that for a friend, I can do that for people I don’t know.” And while many people who have experienced what she went through might not want to set foot in a hospital again, Ms Mulcahy had grown to like the place.

The clincher came when she was interviewed for a midwifery course one day and a teaching job the next. “I came out of the first interview thinking, ‘I want to do that’. I came out of the second thinking, ‘I could do that standing on my head and I’d be bored within a year’.”

After training for three years, she started work at the same hospital where Sophie had been born. There is an educational aspect to her work, “especially with people who are having their first babies”, but she doesn’t yearn for her former career. “I miss having a class - being their teacher and building up a relationship with the children was good - but I don’t miss the marking or report writing.”

Working a rota of 12-hour shifts means she gets time off in the day, so, before Christmas, she managed to see all her daughters’ nativity plays and carol services. “When I was teaching it was hard, even when I was working in the same school.” She recently delivered her 89th baby, but every one, she says, is special. “I still wonder at it; it’s an incredible experience.”

CRAIG BROWN: FOOTBALL MANAGER

Craig Brown is best known as the manager who took Scotland to two World Cups and the European Championship finals. But his career kicked off in the much less glamorous surroundings of Scottish schools in the 1960s, in the midst of a teacher shortage.

“I would be teaching 36 kids in the morning, then they’d go home and we’d have another 37 in the afternoon,” he recalls. “It was horrendous.” At the time he combined work as a PE teacher in Lanarkshire with a flourishing career as a footballer with Dundee, then one of the top teams inScotland.

But midweek fixtures were disrupting his school timetable, so he became a peripatetic teacher in primary schools, continuing to ply his trade as a left-half until injury brought an end to his playing days in the early 1970s.

Mr Brown went into teaching full-time, but was not made to feel welcome.

“In those days male teachers in primary were viewed with suspicion; it was a female domain. PE people were viewed as ignorant acrobats.” He took a degree with the Open University “to get myself some academic respectability” while working as a part-time manager of lower league teams - Motherwell, then Clyde. It was, he says, “a busy time”.

In a teaching career spanning 22 years, he worked as a deputy head and headteacher before becoming a lecturer in primary education at Craigie college in Ayr, where he would observe trainee teachers in the classroom.

“I was once watching a student teaching a grammar class and, afterwards, this wee boy was hanging back. I was sitting there writing my notes and he came over and said to me, acting all confidential, ‘I’ve saw worse’. And this after a grammar lesson.”

After guiding Clyde to promotion, Mr Brown was asked to join the coaching staff of the national squad in 1986, and was made manager in 1989.

Having worked as a teacher - something he has in common with Chelsea boss Jose Mourinho and former Liverpool manager Gerard Houllier - should be an advantage in a job where organisation, motivation and communication are all important. But he says: “When the papers refer to you as a former teacher, that’s not to your credit in football; you’re supposed to be a tough bloke.

“There are similarities between running a school and running a football club. The phrase I used in school and in football is: ‘the standards you set are the standards you get’. You can control attitude, dress and demeanour, but you can’t guarantee results.”

Results were his undoing at Preston North End, where he was sacked as manager last August after a poor start to the season. Since then his witty and erudite opinions have made him much in demand as a radio pundit and newspaper columnist.

JO THORNLEY: PLUMBER

In French it’s le plombier, in German it’s der Klempner. As a teacher of those two languages, Jo Thornley knew the word for plumber was a masculine noun in both. And when, in 1991, she left teaching to train as one, the gender bias was obvious. The only woman on her course at college, once qualified and trading as a one-woman business in Ilkley, an old-fashioned sort of town in West Yorkshire, she encountered prejudice among her customers. “Some men will stand there and watch you; they can’t believe you know what you are doing.”

But that was part of the plan. “I wanted to do something completely different,” she says. “I wanted a job with a man’s wage; I didn’t want to be working in a shop.” When she had returned to teaching after taking a five-year break in the 1980s to bring up her young sons, the national curriculum was being introduced. Suddenly, pipework seemed more appealing than paperwork. “A plumber came into our house to put in a new basin and boiler and I thought, ‘I wish I could do that’. I was brought up on a farm, so I was always very practical and good with my hands. I used to spend ages tinkering about with bikes.”

Before she left her job at a middle school in Keighley, she overheard the deputy head saying how pleased he was that his son had got good grades so “he wouldn’t end up as a plumber”. Now that skilled trades people are so hard to come by, it’s a job that commands a premium. Ms Thornley charges a basic Pounds 40 an hour and, as her own boss, can work when she likes rather than being dictated to by a timetable. What’s more, she says, “to be a plumber these days you need a good understanding of science and technology”. She has just paid for her apprentice - a 30-year-old man - to go to college on day release to get proper training. “Whatever you do it’s important to get the right training,” she says.

“I have been called a trailblazer and an inspiration. If I have inspired others to give up what they are doing and do something they want to do, that’s a good thing. People who stay stuck in a job they don’t enjoy are bound by their own fears, and they shouldn’t be. They should find in their hearts what they want to do.”