NIGEL de Gruchy is a figure who arouses strong feelings.

For Independent columnist David Aaronovitch he “exemplifies the attitude of defensive, backward-looking, reactive and self-pitying conservatism that seems to have prevailed for 20 years among sections of Britain’s hopelessly divided and competing teaching unions... He’s degrouchy, he’s degrumpy. He’s not delightful.”

Well, goodness me. But it is not just Mr Aaronovitch who feels violent at the sight and sound of the leader of the National Association of Schoolmasters Union of Women Teachers. Education and Employment Secretary David Blunkett recently threatened to break both his legs (jovially, of course) when the two met to discuss the NASUWT’s threat to withdraw cover for missing staff.

Nigel, however, can both take it and deal it out. When David Blunkett mused that even the NASUWT might be short of staff in the buoyant labour market, its general secretary sent the Education Secretary an unsolicited job rejection. And when Mr Blunkett urged employers to dock the pay of teachers who refused to cover for absent staff, de Gruchy accused him of “a vicious anti-trade union attitude... reminiscent of the worst days of Tory rule”.

His base is an office high above Covent Garden. Not for Nigel the rural delights of Rednal, the NASUWT headquarters outside Birmingham - he likes to be in the thick of things. His office is within walking distance of Parliament, the Trade Union Congress, the Department for Education and Employment, the radio and TV studios at Millbank, and the law courts where this week, he won a case giving teachers the right to take industrial action to refuse to teach disruptive pupils. He has declined lunch at The TES’s expense in favour of orange juice and sandwiches in his office. Perhaps he is worried about his waistline, still trim at 58. Or perhaps he just doesn’t want to miss the constant telephone calls from the press.

After more than 10 years as general secretary, and 12 years before that as assistant and deputy general secretary, and despite protestations that he wants to step down, he still seems to enjoy doing what he does so well: expressing in perfectly-formed soundbites the gut feelings of the classroom teacher.

Others speak for heads, or tailor their comments to suit long-term political objectives. Nigel speaks for the immediate concerns of the poor bloody infantry, left to sort out the nightmare of an overblown curriculum or the consequences of a policy to cut exclusions which takes no account of the problem of keeping nightmare children in the classroom.

His knack of encapsulating teachers’ feelings, combined with well-publicised victories over the curriculum, exclusions and workload, has produced a steady growth in NASUWT membership over the past 10 years. It is now the 10th largest union in the TUC, with nearly 190,000 members.

But his tactical brilliance has its downside: a lack of deep or strategic thinking, which to some appears to leave a hole where union policy should be. “Nigel is extremely astute but I’ve never thought him a powerful political analyst,” says Peter Smith, of the Association of Teachers and Lecturers. “He’s more interested in tomorrow’s headline than next year’s policy issue.”

As he prepares to work in tandem for a year with Eamonn O’Kane, the next general secretary, Nigel de Gruchy recognises that his successor may have intellectual and organisational strengths he lacks. “I wouldn’t pretend to be a great organiser or manager,” he says. “Why stick yourself in some obscure meeting when you could be out on the TV or radio talking to thousands of embers and millions of the public?” For all his love of publicity, those with long experience of Nigel de Gruchy say he is a private person and a loner. The reasons for that may lie in a fragmented childhood. He was born in 1943, during the German occupation of Jersey, into an old Jersey family - pronounced de Grushi, not de Groochy. His father was a gifted insurance salesman whose dependence on alcohol damaged his career and ruined his marriage. His mother, also Jersey-born, was of Irish stock and determined that her five children should have a good Catholic education. The three boys went to the private De La Salle College. The family fell on hard times and were unable to pay the fees. Nigel’s two elder brothers were sent off to France to train as priests but Nigel refused to go.

When he was 16, the rest of the family went out to Rhodesia to rejoin the father, who was making a doomed attempt to start a new life, but he decided to stay in Jersey with his grandparents. (His father disappeared and was tracked down by his family 25 years later in an old people’s home in Bognor Regis.) After taking a degree in economics and social philosophy at Reading University, he set off in 1965 for the Continent. For three years he travelled, learned French and Spanish and taught English. He was in riot-torn Paris in 1968. And it was there that he met his Swedish-American wife Judy, also in Paris teaching English, and who was later to become a psychiatric social worker.

The two planned to live in the United States, but Nigel was warned he might be eligible for the draft. Vietnam was not a cause he wanted to die for. The two went to London instead, settling in Orpington in Kent. Their son Paul was born in 1975.

Nigel took a job teaching economics at St Joseph’s Academy, a Roman Catholic grammar school in south London, studying part-time for his postgraduate teaching certificate at the Institute of Education. Originally intending to stay at St Joseph’s for only a year, he actually stayed for nearly 10, living through the “traumatic experience” of the change to comprehensive status in the mid-1970s. (De Gruchy supports his union’s anti-11-plus, pro-comprehensive line but harbours “intellectual reservations” about whether one type of school can cater for all.) Once a teacher within the Inner London Education Authority, Nigel soon became involved in union politics. This was the time of disputes over Harold Wilson’s pay policy. After speaking up at an NAS meeting in the local pub, he was hooked. Within months he was branch secretary, then became London secretary and served on the national executive from 1975 to 1978. In 1978 he joined the union staff as an assistant secretary - but his real role was that of press officer.

His greatest single triumph as general secretary was, he thinks, the union’s legal victory against the borough of Wandsworth over teachers’ workload and national curriculum testing, which led directly to the Dearing revisions. His most bitter disappointment has been the failure to establish a social dialogue with New Labour.

A self-confessed workaholic until several years ago, he says he now takes life a little easier. When he steps down as general secretary next April, he will continue to serve on the executive of Educational International, a body representing 23 million teachers from 140 countries. He is also likely to become president of the TUC in 2003, the first teacher union leader to do so since Fred Jarvis of the NUT.

When he really does retire, this restless man promises to “give leisure a good try”. He and his wife Judy might move to Jersey or somewhere warmer so that he can play golf and indulge the love of swimming and beach life he acquired in his childhood.