There is much more to this than the Big Idea he has been banging on about for some time - a new Open Sector to replace the old direct grant scheme. Open schools would have to offer all their places for admission “by ability and aptitude”. Fees would be charged, subject to a means test. The scheme would be funded directly by central government and open to all independent day schools - boarding schools would be financed privately.

Many independent day schools, including most of the former direct grant schools, would be tempted. They would get the cream of the 11-plus intake and, therefore, the top places in the league tables. Schools which stayed outside would feel the draught. Provided their “independence” was guaranteed, governors would find it hard to say no - if, that is, they could trust the Government of the day to pay their steadily rising fees. (Look how the present Government has cheated on the Assisted Places scheme.) Every 25 years or so - Fleming, Newsom-Donnison, now Walden - someone revisits the social divide at the centre of the education system: the expensive private sector taking 7 per cent of pupils and the underfunded maintained sector where the 93 per cent of “other people’s children” go. Walden believes that till the professional and managerial classes send their children to state schools, the state schools will always he second-rate. It is, as I say, a familiar left-wing thesis. Coming from the Right, it has added force.

The politics of such a scheme are fraught with difficulty - fees at such schools would be roughly twice what is spent on equivalent pupils in maintained schools. If this can be justified for the fortunate few, why not for others, equally deserving?

By itself such a scheme would do little to break down the class barrier. But Walden is right: simply pointing out flaws in reform packages is just a way of defending the status quo. Revolutionary change is not on, so the trick (if there is one) must be to find step-by-step measures to bring unification within range.

This book puts the Open Sector idea in a context of wider reform. Walden is not really a free-market-in-education man. His priorities are to get rid of the residue of progressive teaching methods and Dewey-influenced educational theory and to introduce more differentiation and diversity into secondary education.

He would obviously like a selective system, with grammar schools and a new generation of high quality technical schools. But he knows you cannot simply go back to pre-1965. He wants more overt differentiation within schools as well as more external selection. He has little to offer the “unselected” majority except better basic teaching.

With no illusions about the costs, he puts a Pounds 5 billion price tag on what needs to be done. His Open Sector would cost Pounds 1bn, less the saving on the Assisted Places scheme which it would replace; nursery schools for all would cost a net Pounds 500m; a new technical sector, another billion. To this would be added an extra l0 per cent on the teachers’ pay bill (with various strings attached). He tries to justify all this by painting an especially horrific picture of present failure.

If he takes off into fantasy at times, it is the fantasy of someone who dreams of a better England. And he must be right about the insidious damage done by having two separate, class-based education systems.

The best answer would be to do for all post-14 education what was done for higher education after the war - open it all up to everyone according to ability. Before the war, access to the private chartered universities was for those who could matriculate and pay the fees. After the war the financial barriers came down. No one would now advocate going back. We need to mobilise all schools, including the independent secondary schools, and use them for the nation. It wouldn’t cost any more, but it would mean splitting the bill up differently.

Stuart Maclure is a former editor of The TES