It is good to know that, by the time summer’s rains give way to autumn’s hurricanes, what Xenophilius Lovegood had to say to a scar-faced boy wizard concerning the Resurrection Stone and the Elder Wand will be informing the actions of our Liberal Democrat MPs. It feels more reassuring, however, that Tory MPs were planning – less demotically but more virtuously – to plough through William Hague’s biography of William Wilberforce. Don’t you agree that it is so important that our rulers should have a proper sense of history?

Now substitute the word “physics” for “history” in all those sentences that seem to appear four or five times a week, uttered by this academic or that think-tank, and lamented over by columnists and leader writers. Is it vital that every child should have a grounding in physics? Is it necessary that every senior politician should have a keen understanding of physics? Is the operation of the physical world an essential part of comprehending the world we live in? Is it heck as like.

Is the physics curriculum too narrow? Is it repetitive? Is it well taught? Do pupils give up physics too early? Who knows? But everyone with more than two GCSEs and a humanities degree to rub together has an opinion on the teaching of, and learning from, history.

Yesterday it was Katherine Tattersall, of the Chartered Institute of Educational Assessors, predicting that history might die out as an A-level subject because it’s not taught compulsorily to children over 14. Its place would be taken, she seemed to suggest, by photography (oh yes), media studies (boo) or geography, surfing the wave of popular interest in climate change. I seem to recall that the Tories had been considering advocating extending compulsory history to the age of 16, so that you could legally give it up on the same day as you had your first legal gay experience.

Back in 1968, in a London grammar school, I had to choose between geography and history, and I don’t recall the life of the nation hanging on my decision. Since then, however, history has become a heavily politicised field of battle. For a start it is now required, in a way it never was before, to instil national consciousness into our young folks, giving them what David Willetts, in his education sojourn on the Tory benches, called “national memory”.

I am not opposed to doing this, or against retelling the great narratives of this country’s story, its heroes and villains, from slavery to Dunkirk – as long as one understands that this is only one kind of history. It does strike me, however, that the seven years from 7 to 14 ought to be enough time to fulfil this duty of citizenship.

What worries me most about this discussion, however, is the idea of history as uncontested. I don’t mean by this that everything is relative, and that the Holocaust or Sir Francis Drake didn’t really, in some important sense, actually exist. As I look at the hundreds of books on my shelves I see just how complicated is the business of deciding causality or relative importance. Is it extraordinary, for instance, that the US delayed until December 1941 before entering the Second World War, or more extraordinary that in 1940 it helped faraway Britain at all?

Every now and again, since it became known that I was working on a television history of the Blair years, someone will tell me that Tony Blair had “no sense of history”, and that this accounted for his mistakes. One or two have advised me to look at the writings of David Marquand, who last year castigated the former Prime Minister and his “appallingly dangerous” ignorance of history, for exaggerating the threat from terrorism. “No one,” Professor Marquand declared, “with any knowledge of 20th-century history could possibly believe that the attack on the twin towers ‘changed everything’ ” and “no one with a sense of history could possibly have thought that 9/11 marked a historic turning point”.

Professor Marquand’s suspiciously contemptuous anger seemed on the surface to have two barely related causes: the first that terrorism should be regarded as being an existential threat, as was the threat from Hitler or even from Khrushchev, and the second that Blair should “demean the memory” of Churchill and the fight against Nazism. It was an interesting elision, suggesting that the professor was complaining as much about his generation’s history being superseded, as he was about an interpretation of facts.

But is it so preposterous to suggest that a global ideology that justifies the use of limitless violence against civilians, and whose adherents are immensely inventive (if not always competent) in discerning methods of delivering that violence, could present an “existential” threat? Suppose for a moment that we had a run of bad luck, and that the various unsuccessful plots to bomb Britain, including July 21, 2005, had in fact succeeded. Suppose Glasgow airport had had a queue of travellers obliterated, that several nightclubs full of youngsters had been destroyed, that every brown doctor and driver had become, in the eyes of their fellow citizens, a potent menace. What does Professor Marquand imagine might have happened then?

Another objection to Mr Blair’s historicism was that he didn’t know enough history to understand the context in which he sought to fight terror. He only saw the present, and couldn’t comprehend why everyone in the Middle East (barring the Israelis, who don’t count) would have good cause to hate us. “History would have told him,” wrote Edward Pearce, “that bossed and humiliated people rebel . . . He would know more generally that occupied countries take to the experience very badly.”

Except, of course, where they don’t. He would know (circa October 2001) that you cannot fight a successful war in Afghanistan, except when you can. He should have understood – as he was advised – that the problems of Northern Ireland, rooted in historical antagonism, were intractable, and that the people of the Balkans were unhelpable. In 2001 he should have bet all his money on Spurs winning the Premiership, because the year ended in a “one”.

No one who knows anything about history should ever talk about “the lessons of history”. It may be safer that some of our politicians are spending their summers learning how to liberate house elfs.

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