It is easy to forget, in a landscape so timeless and fetching, so companionably rooted to an ancient past, how easily it is lost. The panorama before me incorporated electricity pylons, scattered housing estates and the distant sunny glints of cash and carry warehouses. Far worse, the dense, carefully knitted network of hedgerows was showing distinct signs of becoming frayed and disjointed, like the pattern on a candlewick bedspread that has been picked off by idle fingers. Here and there fragments of overgrown hedge stood stranded and forlorn in the midst of otherwise featureless fields.

 Did you know that between 1945 and 1985 England lost 96,000 miles of hedgerows enough to girdle the earth four times? So muddled has been government policy towards the countryside that for a period of twentyfour years farmers could actually get one grant to plant hedgerows and another to grub them up. Between 1984 and 1990, despite the withdrawal of government money to plough up hedgerows, a further 53,000 miles were lost. You often hear it said (and I know because I once spent three days at a symposium on hedgerows; the things I do to keep my children in Reeboks) that hedgerows are, in fact, a transitory feature of the landscape, a relic of the enclosure movements, and that trying to save them merely thwarts the natural evolution of the countryside. Indeed, increasingly you hear the view that conservation of all types is fussy, retrograde and an impediment to progress. I have before me as I write a quote from Lord Palumbo arguing that the whole vague notion of heritage 'carries the baggage of nostalgia for a nonexistent golden age which, had it existed, might well have been the death of invention', which is so fatuous it breaks my heart.

 Quite apart from the consideration that if you followed that argument to its logical conclusion you would tear down Stonehenge and the Tower of London, in point of fact many hedgerows have been there for a very, very long time. In Cambridgeshire, I know of a particularly lovely hedge, called Judith's Hedge, that is older than Salisbury Cathedral, older than York Minster, older indeed than all but a handful of buildings in Britain, and yet no statute stands between it and its destruction. If the road needed widening or the owners decided they preferred the properly to be bounded by fenceposts and barbed wire, it would be the work of but a couple of hours to bulldoze away 900 years of living history. That's insane. At least half the hedgerows in Britain predate the enclosure movements and perhaps as many as a fifth date back to AngloSaxon times. Anyway, the reason for saving them isn't because they have been there for ever and ever, but because they clearly and unequivocally enhance the landscape. They are a central part of what makes England England. Without them, it would just be Indiana with steeples.

 It gets me a little wild sometimes. You have in this country the most comely, the most parklike, the most flawlessly composed countryside the world has ever known, a product of centuries of tireless, instinctive improvement, and you are half a generation from destroying most of it for ever. We're not talking here about 'nostalgia for a nonexistent golden age'. We're talking about something that is green and living and incomparably beautiful. So if one more person says to me, 'Hedgerows aren't really an ancient feature of the landscape, you know,' I shall very likely punch him in the hooter. I'm a great believer in Voltaire's famous maxim, 'Sir, I may not agree with what you say, but I shall defend to the death your right to be a complete asshole,' but there comes a time when a line must be drawn.I struck off down a wooded back lane to Snowshill, three miles away. The leaves were golden and rustly and the sky vast and blue and empty but for an occasional slowmoving wedge of migrating birds. It was a wonderful day to be abroad the kind of day that has you puffing your chest and singing 'Zippity Doo Dah' in the voice of Paul Robeson. Snowshill drowsed in the sunshine, a cluster of stone cottages gathered round a sloping green. I bought an entrance ticket to Snowshill Manor, now in the hands of the National Trust but from 1919 to 1956 the home of an eccentric character named Charles Wade, who devoted his life to accumulating a vast and unfocused assortment of stuff, some of it very good, some of it little more than junk clavichords, microscopes, Flemish tapestries, snuff and tobacco boxes, maps and sextants, samurai armour, pennyfarthing bicycles, you name it until he had filled his house so full that there was no room left for him. He spent his last years living happily in an outbuilding, which, like the house, has been preserved as it was on the day he died. I enjoyed it very much, and afterwards, as the sun sank in the west and the world filled with long shadows and a vague, entrancing smell of woodsmoke, I hiked back to my car a happy man.

 I spent the night in Cirencester and the next day, after a pleasant look around the little Corinium Museum with its outstanding but curiously littleknown collection of Roman mosaics, coins and other artefacts, drove on to Winchcombe to see the real thing in situ. On a hill above Winchcombe, you see, there is a littlevisited site so singular and wonderful that I hesitate even to mention it. Most of the relatively few visitors who intrude upon this tranquil corner of the Cotswolds generally content themselves with a look around Sudeley Castle or a hike to the remote hump of the famous Belas Knap long barrow. But I headed straight for a grassy hillside path called the Salt Way, so named because in medieval times salt was conveyed along it. It was an enchanting walk through open countryside, with long views across sharply defined valleys that seemed never to have seen a car or heard the sound of a chainsaw.

 At a place called Cole's Hill the path plunged abruptly into a seriously overgrown wood, dark and primeval in feel and all but impenetrable with brambles. Somewhere in here, I knew, was my goal a site listed on the map as 'Roman villa (remains of)'. For perhaps half an hour, I hacked through the growth with my stick before I came upon the foundations of an old wall. It looked like nothing much the remains of an old pigsty perhaps but a few feet further on, all but obscured by wild ivy, were more low walls, a whole series of them, on both sides of the path. The path itself was paved with flagstones underneath a carpet of wet leaves, and I knew that I was in the villa. In one of the relict chambers, the floor had been carefully covered with plastic fertilizer bags weighted with stones at each corner. This is what I had come to see. I had been told about this by a friend but had never really believed it. For underneath those bags was a virtually complete Roman mosaic, about five feet square, exquisitely patterned and flawlessly preserved but for a tiny bit of fracturing around the edges.

 I cannot tell you how odd it felt to be standing in a forgotten wood in what had once been, in an inconceivably distant past, the home of a Roman family, looking at a mosaic laid at least 1,600 years ago when this was an open sunny space, long before this ancient wood grew up around it. It is one thing to see these things in museums, quite another to come upon one on the spot where it was laid. I have no idea why it hadn't been gathered up and taken away to some place like the Corinium Museum. I presume it is a terrible oversight, but I am so grateful to have had the chance to see it. I sat for a long time on a stone, riveted with wonder and admiration. I don't know what seized me more, the thought that people in togas had once stood on this floor chatting in vernacular Latin or that it was still here, flawless and undisturbed, amid this tangle of growth.

 This may sound awfully stupid, but for the first time it dawned on me in a kind of profound way that all those Roman antiquities I had gazed at over the years weren't created with a view to ending up one day in museums. Because the mosaic was still in its original setting, because it hadn't been roped off and placed inside a modern building, it was still clearly and radiantly a floor and not merely some diverting artefact. This was something meant to be walked on and used, something that had unquestionably felt the shuffle of Roman sandals. It had a strange kind of spell about it that left me quietly agog.