The backroom Blairite who knows the answers about life after Blair

The more personalised the election campaign becomes, the more dominated by the presidential Blair, the more insistent becomes the question: what comes after him? The fact that we know he is fighting his last general election throws the spotlight forward in a way that would not happen if we thought he might stay on. We have worried endlessly at one aspect of this question, namely who comes after Tony Blair. Just as important, although it is related, is the "what".

Hence the significance of the book published this week by Peter Hyman, 1 Out of 10, which tells the story of how he left Downing Street to work as a teaching assistant in the Islington school to which Blair did not send his children. Hyman's is not a household name but, for nearly a decade, he was Blair's main speechwriter. As he observes in the book, politics is all about words. The person who puts the words in a leader's mouth is therefore in a strangely influential but subordinate position. He wrote the phrase "power, wealth and opportunity in the hands of the many not the few" in Labour's new Clause Four. And he was not only a wordsmith, he was what is known in New Labour speak as a "communications strategist". He devised the original pledge card before the 1997 election - the version for the 2005 election was unveiled last week - and he invented the Grid, the simple A4 matrix for planning each week's announcements, speeches and news events.

So journalists and MPs were justified, when the book was trailed last week, in focusing on one line from it, in which Hyman supports higher taxation for the better off. When it turns out that His Master's Voice disagrees with His Master, it is news. But tax is only a part of a bigger disagreement. The book details the great struggles in the Prime Minister's office over two party conference speeches, in 1999 and 2003.

In 1999, Hyman and Alastair Campbell were delighted when Blair finally agreed to take the fight to the enemy with a speech attacking the "forces of conservatism". This was a criticism of conservatives of the left, but the main thrust was against the right. The Tory press responded with fury - the long media honeymoon was suddenly over. "It was all too much for Peter Mandelson and to a lesser extent Tony," complains Hyman. "We started back-tracking ... We would never again make a head-on assault on the right. We would return to progressive politics by stealth."

Hyman quotes Blair's response in a note in April 2000: "There is no easily identifiable group - saving perhaps the hereditary peers and that is very limited - that can be described as 'holding Britain back'. To invent one, or worse single out some group just to have one, will cause more problems than it solves. It doesn't feel right to me."

The 2003 conference speech was written in a very different situation, in which Blair had plenty of enemies, mostly among natural Labour supporters. Hyman sought to use the speech to define a "new phase" of New Labour. But Blair and Hyman had rather different views of what the new phase meant. For Blair it meant intensifying the revolution. For Hyman, worried about the shortage of revolutionaries, it was a chance, after six years in power and having established its economic competence, for the party to be more openly social-democratic.

Hyman did not leave Downing Street because he lost that argument, but this is where his story becomes really interesting. Politicians often try to find out what "real" life is like. They listen to focus groups. They visit schools, hospitals and the set of Coronation Street. Some of the less busy ones go on the dole for a week or take the place of lone parents for television programmes. But Hyman's experience of writing speeches about public service reform and then going to work in a public service - for more than a year so far - is unusual.

The result is a partial recantation of the New Labour faith. As a speechwriter he had been excited about the idea of "personalised learning". As a teaching assistant he was told: "What do you think a good teacher does?" He concludes that "our approach to political strategy had been based on three things: momentum, conflict and novelty", which was "entirely the wrong one for convincing front-line professionals" - the people who have to deliver for a government - who require "empowerment, partnership and consistency". He is also critical of the rules for academies that give private-sector sponsors a majority of the school's governors in return for putting up £2m of a total £30m investment - although he supports the plan for his school, Islington Green, to become an academy later this year.

Yet Hyman's is only a partial recantation. His disagreement is with how the policies are sold rather than, fundamentally, with the policies themselves. He thinks academy status is the best chance for Islington Green. As someone interested in words, he points out that "comprehensive" is contaminated because it is applied to schools such as Islington Green whose intake is anything but, because of middle-class flight to other boroughs and to the private sector.

Here it may be possible to discern the outlines of a post-Blairite synthesis that is neither a retreat to Old Labour nor simply an intensification of conflict and novelty. If the promise of 200 new academies on the latest incarnation of the pledge card can be sold to the teachers and head teachers who have to deliver it as the means to realise the values of the comprehensive ideal, then we will indeed enter a "new phase" of politics. Similar principles apply in the NHS, where many doctors still regard patient choice as a threat rather than an opportunity.

That is why Gordon Brown is on to something when he sets out his post-Blair stall promoting the "public service ethos". But the Chancellor is wrong to suggest that this is the alternative to diversity in the supply of public services. Giving parents and patients choice is essential, but it will only work if education and health service providers feel that they are trusted by central government to innovate and experiment. That is starting to happen, but New Labour needs a change of language to inspire professionals to seize the opportunities devolved to them.

Of the two big political books so far this year, Hyman's is essential reading for anyone wanting to understand the shape of New New Labour. Robert Peston's biography of the Chancellor last month was surprisingly thin on Brown's vision for the future. The only two policies mentioned in Peston's summary were an elected House of Lords and a new procedure for going to war, which is the same as the vote actually held before the Iraq invasion. One of the Prime Minister's advisers was withering: "Is that it?"

Hyman's book is important because he tries to relate political rhetoric to classroom reality. In doing so, Blair's former speechwriter has rendered the party a most valuable service.