Mick Waters, widely seen as one of the most charismatic figures in English education, is leaving the Qualifications and Curriculum Authority after four years at the heart of the debate over the future of teaching.
Mr Waters, the architect of the new secondary curriculum and a man described two years ago as "the biggest champion for children out there", is to stand down next April, when the first phase of the Government's primary review, to which he contributed extensively, finishes.
His departure will leave a major gap at the top of the new Qualifications and Curriculum Development Agency, which is the replacement for the QCA now that its regulatory functions have been transferred to Ofqual.
There have been tensions between the QCA and the Government, and Mr Waters, in his late fifties, said he was not interested in succeeding his boss, Ken Boston, as chief executive when Dr Boston's contract runs out next summer.
The Government recently handed responsibility for reviewing the primary curriculum not to Mr Waters but to Sir Jim Rose, a QCA board member. But, speaking exclusively to The TES, Mr Waters, director of curriculum at the QCA, said there was "nothing political", behind his decision to go.
He said: "When I came to the QCA, I agreed to stay for four years. That time will be complete in April, and most of the programmes I have been working on reach their natural conclusions at that point."
However, many teachers will greet the news with shock. Mr Waters has spent much of his time promoting his call for professionals to be given more freedom to tailor the curriculum to their pupils' needs. The reception was often rapturous. Mick Brookes, general secretary of the National Association of Head Teachers, said: "He's quite a giant in the whole educational arena.
"His presentations to my colleagues have always been received with absolute enthusiasm."
Mr Waters spearheaded the review of the secondary curriculum, which has led to a paring-down of subject content and encourages teachers to make links between subjects. He has also been QCA's lead in providing evidence for Sir Jim's primary review.
He has not been universally popular. Some secondary subject teachers worried that he emphasised cross-curricular work at the expense of their disciplines. There has been speculation that his stance has not been popular with ministers.
In 2006, Paul Jones, chairman of the Devon Association of Primary Heads, told The TES that Mr Waters was "the biggest champion for children out there. Schools are bursting to try things out with the curriculum. Now they feel they have official backing." Mr Waters said he had yet to finalise his plans.