After more than a quarter of a century of well-chosen soundbites and tireless lobbying, this summer will see one of education's best-known protagonists finally switch off his mobile telephone.
It may be a much-used cliche, but the retirement of the leader of the largest headteachers' union really will mark the end of an era.
Education secretaries have come and gone - 12 of them to be precise - but David Hart has always been there, listening to his members and ensuring their views are heard in the media and at the highest level of government.
The National Association of Head Teachers was a very different organisation when Mr Hart took over as general secretary in 1978. John Swallow, among the national council members who appointed him, said: "He put the association on the national scene. Before he took over it was a small parochial body. It looked after the welfare of members perfectly well but there was no education policy or agenda at all and no involvement on the national stage, talking to ministers and journalists."
Mr Hart had advised the association as a solicitor for the London law firm Royds Barfield Back. But the appointment of a non-headteacher attracted plenty of internal criticism. When his lack of in-school experience was put to him during his interview for the post he replied: "I have got more than 20,000 experts in the NAHT."
It is an approach he has stuck to ever since, priding himself on his ability to understand his 40,000 members' worries, and that it is what he expects to miss the most. "The face-to-face contact you get with NAHT members around the country is the best part of the job," he said. As well he might, having met his wife Frankie, then NAHT president in north-east Cumbria, at a branch meeting in 1992.
A shy man, and perhaps not the most clubbable figure, he has nevertheless achieved much of the association's influence through the close working relationships he formed with successive education secretaries.
Mr Swallow, NAHT president in 1983, was at the same table for many of the meetings and saw a great persuader at work. "He was very controlled, calm and balanced ... He mastered his brief, his arguments were logical and he was strong."
Baroness Morris, education secretary from 2001-2002, described Mr Hart as a towering figure in education. "He is a gentle, quiet man. I have never heard him raise his voice and he has never been nasty or malevolent. But he really has got a steely frame underneath. He's no pushover."
Her Conservative counterpart, Baroness Shephard, education secretary from 1995 to 1997, remembers someone who "always fought hard for his cause but was very civilised to deal with".
He has not, however, been averse to the occasional piece of a mischief, a master at stirring things up with a well-timed word in a journalist's ear.
Asked for career highlights, Lady Shephard lists the big impact Mr Hart's association had on the late 1980s Conservative reforms which gave heads more autonomy through the local management of schools. Mr Hart was awarded the OBE in 1988.
He believes his strengths include his ability to respond on behalf of NAHT members in a way that reflects their mood. But he has done more than that.
Often several steps ahead of his members, he has led them into a transformation of the role of the head, and had to work hard to persuade his largely primary membership to forsake the local authority comfort blanket for increasing autonomy.
So it must be a great regret for him that as his general secretaryship closes he finds himself at odds with his association after it ignored his advice and voted to pull out of the workforce deal.
Nigel de Gruchy, NASUWT general secretary from 1990-2002, said: "He led with great skill for many years and has been almost solely responsible for the NAHT punching above its weight."
It will be hard for anyone to match the excellent relationship Mr Hart has built with the media through his round-the-clock availability. It has been rare to see him without a mobile phone clamped to his ear. "It goes with the territory and if you are not prepared to be accessible all day every day, then don't bother taking it on," he said.
That may not be quite the view that Frankie takes, having had her honeymoon interrupted by her husband's dedication to duty. This September will see her patience finally rewarded. Mr Hart still expects to do some education consultancy work, but the couple should be able to enjoy their shared love of horse-riding - with the mobile switched off.
"Giving power to parents who lack responsibility is like putting an alcoholic in charge of a bar." (Pouring cold water on Education Secretary Ruth Kelly's pre-election push for parent power earlier this year)
"Where has the role of parents gone? Why aren't they telling their children where acorns come from and how to tell a chicken from a pheasant?" (On a survey revealing children's ignorance of rural matters, 2000)
"How can it be that a young person is at risk of custody if they steal a mobile phone in the street, but cannot be removed from school if they do the same in the corridor?" (A call for more support for heads on permanent exclusions, 2002)
"Education, education, education may be the motto. But teachers, teachers, teachers are the key." (Addressing NAHT conference delegates, 1998) "What a difference a new chief inspector makes." (Welcoming the first Ofsted annual report since Chris Woodhead's departure, 2001)
"The budget is all promise and not a lot of delivery. If the comprehensive spending review does not come up trumps on matters such as workload and performance-related pay, then all hell will let loose." (A warning to the Treasury, 2002)