Writing about Greece, writing about Rome, writing about Persia (with apologies to all Zoroastrians), I was dealing with gods that are pretty much extinct. Writing about Christendom in Millennium, however, I was not. The contrast was brought home powerfully to me yesterday, when I chaired an event at the Frontline Club in Paddington, which had as its theme what the journalist Paul Marshall has termed his profession's "blind spot": its failure to get religion. His case, one which he and several others have made with great force and clarity in a fascinating new book, is that journalists are blinded by ignorance and disdain from taking religion seriously, and as a result can miss the point of fundamentally important news stories – whether it be the rise of Islamic terrorism or the course of recent US presidential elections or the politics of aid to Africa. Marshall's paradigm, however, is principally an American one, featuring as it does a liberal, secular elite stood apart from the great mass of a God-fearing population – and I do not think that it applies to Britain. Here, even the religious can often seem embarrassed to admit to anything so un-ironic as sincerity or an interest in the spiritual - and there is a substantial minority (a whole third of the population, according to a poll I heard on the news yesterday), who seem actively to detest everything to do with religion. This – quite apart from serving to boost Richard Dawkins' royalty cheques – means that the task of the historian who wishes to argue for the significance of the Christian origins of our ethical and social presumptions is of a quite different level of difficulty to that which confronts the classicist, say, who has to make the case for the abiding relevance of ancient Greece or Rome. Put simply, the Christian god – and Allah too, of course – are threatening to many people in a way that Zeus or Jupiter are not.

I have had personal reason to appreciate this. Last autumn, to coincide with the publication of Millennium, I wrote an article in the New Statesman arguing for the significance of the Gregorian revolution of the 11th century for the present - exactly the same order of product placement that I had previously done for Rubicon and Persian Fire. Rather to my surprise, however, the reaction of the magazine's readers verged on the outraged - so much so, indeed, that the delighted editor promptly invited me to write a reply. This, of course, did little to make his readers any the less indignant. Still - every cloud has a silver lining - because evidently it was the blowback from these two articles which got me onto the panel at the Blind Spot event – an opportunity I would really not have wanted to miss. To come straight from reading Ibn Ishaq on the sanctuary of Mecca, and meet a Muslim scholar passionately distraught at the fate being meted out to the antiquities of the city, courtesy of the Saudi authorities at their most brutally Cromwellian, was to feel anew the burning relevance of studying ancient history. No longer was it something academic, but something viscerally, passionately felt. What is faith, after all, but an attempt to transcend the diurnal, the contemporary? To feel a sense of communion with all those countless vanished millions of souls who have practised rites, and said prayers, and nurtured beliefs that, it may be, have a continuity across the span of entire millennia? To shrink the centuries - is that not precisely what the historian aims to do as well?

Which leaves me reflecting how sad it is that Gaiman's novel was indeed just a work of fantasy, and that I will most likely not be bumping into Athena in the British Library. The ache to believe can sometimes come as such a surprise that it serves to jolt. Last week, when I was in the Lakes, I climbed Helvellyn - a lunatic project as it turned out - because the peak, which could only be approached along a razor sharp ridge of rock, was covered in ice and snow, and lashed by gale-force winds. Everyone else I meet with had crampons and ice-picks and compasses - whereas I had nothing except a gnawing feeling that I had been a tit, and was most likely going to die. Fortunately, however, after what seemed a very long half hour scrabbling through snow on my hands and knees, I made it to the opposite end of the ridge. There I found a memorial stone which had been raised to a Victorian climber: falling to his death, it seemed, his dog had stood loyally over his corpse for three whole months, until finally the body was found. In ancient Greece, perhaps, he would have been worshipped as a hero; in medieval times, as a saint. Either way, standing there before the memorial stone, I found myself wishing that it had been a shrine of some kind: something that I could pray to, just to set my racing heart at rest. But, of course, it was nothing of the kind - and so there was just me, the memorial stone, the wind, the mountain, and nothing else. 

"Whither is fled the visionary gleam?" as they like to say in Cumbria. "Where is it now, the glory and the dream?" Hey hey, where indeed?