The bushy-bearded campaigner, dubbed “The Ayatollah of Bolton” by one former general secretary, has been pressing for teachers to be relieved of administrative tasks since his first union conference in 1973.

“I spent 10 years persuading the union to go for workforce remodelling, and the union’s spent 20 years campaigning on it. It has been a lifetime, so I’m chuffed to bits the deal’s finally happening,” he said.

Mr Boone, 57, the union’s assistant secretary for industrial relations, describes himself as an “unreconstructed trade unionist and typical union dinosaur”.

He began work as a secondary school music teacher in his home town of Bolton at the age of 24 after chronic asthma cut short his career as a research scientist with ICI.

When the larger-than-life activist attended his first union conference in Eastbourne, his distinctive beard was flaming red and he was so slim you could play tunes on his ribs.

Over the three decades that followed he has only missed the conference twice.Delegates have heard him speak on a range of issues from teachers’

pay and conditions to the dangers of foxes entering the Channel Tunnel.

He is a stalwart of the conference’s late-night social scene, belting out songs in a bluesy voice while playing the piano or one of the other half-a-dozen instruments he has taught himself. His repertoire has expanded over the years to take in songs from the Beatles to Oasis.

Mr Boone insists changes to the union, including the merger of the all-male National Association of Schoolmasters with the Union of Women Teachers in 1976, have made it a friendlier organisation.

“When I first came there was a lot of plotting in corridors, midnight meetings in hotels discussing how we were going to sandbag the national executive,” he said.

“It didn’t achieve anything. I miss the passion, but I don’t miss the lack of trust.”