Eamonn O'Kane, general secretary of the National Association of Schoolmasters Union of Women Teachers, died of cancer on Saturday, aged 58.
He led his union for only two years but played a central role in creating a partnership with government which has transformed the way teachers' pay and conditions are negotiated.
Mr O'Kane was a popular and respected figure in the education and union world. Tributes from colleagues, ministers, rival union leaders and educationists recall him as a passionate, intelligent and tough negotiator able to charm those on both sides of the table with his humour and good nature.
Tony Blair, Prime Minister, said: "Eamonn O'Kane was a very distinguished leader of his union who gave an enormous amount to the teaching profession.
His untimely death is very sad."
Mr O'Kane was born in August 1945 into a Catholic Belfast family. He attended St Malachy's College in the city and went on to Queen's University in Belfast, where he graduated in 1968 with a degree in economics and history.
These were the subjects he taught during a 20-year teaching career in north Belfast that began in 1969 at St Patrick's secondary school on the Antrim Road.
During this period the province's troubles were never far away - he once confiscated what looked like a ball from one of his more "challenging" pupils, only to find it was a live blast bomb.
A committed trade unionist, socialist and lifelong Labour party member, Mr O'Kane helped to bridge the religious divide in his home city by aiding the non-sectarian NASUWT's rise to become Northern Ireland's biggest teaching union. In 1982 he became chairman of the union's salaries committee and in 1987 its president. During those years Mr O'Kane struck up a friendship with Nigel de Gruchy, who would often give him lifts to Heathrow airport after attending national executive meetings.
By the end of the decade, the pair had emerged as the two leading contenders to take over as general secretary from Fred Smithies, who retired in 1990. It was Mr de Gruchy who won the backing of national executive and was elected general secretary, while Mr O'Kane agreed to stand as his deputy. As one trade union figure put it at the time: "Nigel is the mouth and Eamonn is the brains of the NASUWT."
It would be another 12 years before he finally took over the reins. His leadership got off to a bad start at the 2002 NASUWT conference in Scarborough, when angry activists slapped down his proposals for merger between the three main teaching unions.
But his attention was soon taken up by the negotiations with the Government, employers and other unions on teacher workload that led to the signing of the school workforce agreement in January 2003.
By then the National Union of Teachers had dropped out, leaving Mr O'Kane as leader of the largest remaining teaching union in the negotiations.
For anyone who knew Eamonn O'Kane personally it is his good humour, knowledge and all-round zest for life that will be remembered. He was not just a union man: he had a love of literature, opera, history and football.
His wicked sense of humour and infectious snorting laugh enlivened any company.
Joe Boone, NASUWT assistant secretary for industrial relations, said: "He had a great sense of humour and he talked 19 to the dozen: he was like Frank Carson. I have lost a great mate."
Mr O'Kane is survived by his second wife Daphne, the retired head of a special needs centre and NASUWT activist, and his two daughters, Adrienne and Catherine, from his first marriage to Geraldine, who also survives him.