Map Addict. Mike Parker

So, as eager not to appear bad losers as had the French been on the Greenwich vote, the Americans and British then ostentatiously supported the metric system in the subsequent vote. In fact, no one voted against it—not that that made the faintest bit of difference in actually making it happen.

      Flushed with their pyrrhic victory, the French demanded a further adjournment to the conference, which briefly reconvened two days later before its final adjournment, for nine days, in order that the conference protocols could be drawn up, in English and, of course, in French. On the first of November, a month to the day since the delegates had first gathered, the conference closed in a mutual orgy of back-slapping and vainglorious speeches about how the international community was united as never before and that they had made history. Thankfully, the sagging balloon of hot air was peremptorily pricked by the very last contribution noted in the conference minutes: the ever vocal M. Janssen of the French delegation complaining about the standard of French used in their translations.

      As expected, the French reaction to the conference’s decision was to ignore it for as long as they possibly could. The Paris Meridian was still marked as 0° on French maps until 1911, and even beyond that, they kept refusing to refer to the notion of Greenwich Mean Time, preferring instead to name the concept the altogether snappier ‘Paris Mean Time diminished by 9 minutes 21 seconds’. It’s a shame it didn’t catch on: PMT has such an appropriate ring to it for matters of timekeeping. Even though the Paris Meridian has long been shunted into the sidings, the French still keep polishing it and showing it off to the world like a priceless relic. One of their main millennium projects was to plant lines of trees the entire length of France along their old meridian line. It might no longer be functioning, but hey, you could see it from space, or at least if you look closely enough on Google Earth in a few decades’ time. To a chippy Brit (and, when it comes to any dealings with the French, that’s most of us), the project smacked of dismissive looking down the Gallic nose at the lack of presentational flair that attends our meridian line.

      The world’s timekeeping and cartographic staff it may be, but as the Prime Meridian enters Britain in the retirement town of Peacehaven on the Sussex coast, it’s marked only by a dowdy obelisk and the Meridian Centre, a deathly 1970s shopping mall with the unmistakable aroma of incontinence. Two hundred and three miles due north, it leaves English soil in similarly dreary fashion, on a beach just south of the Sand-le-Mere caravan park, near Tunstall on the Holderness coast of Yorkshire’s East Riding. Britain’s bleakest coast is also

       Substance over style: where the Prime Meridian enters England at Tunstall, East Yorkshire

      the fastest-receding in Europe, where houses and roads tumble regularly over the edge, leaving their forlorn traces to be washed over by a freezing sea the colour of a river in high flood. In the circumstances, the great local millennium project—placing a huge carved boulder on the cliff top to mark the point at which the global meridian arrives in its home country from the North Pole—was something of a triumph of optimism over experience. Instead of lasting the full thousand years, it managed just three, disappearing over the muddy cliff in a storm in January 2003. In between these two inauspicious gateposts, as well as the whistles and bells of Greenwich itself, the meridian is marked by a number of plaques, columns, archways and, in Cambridgeshire, a line of daffodils planted by Boy Scouts. It’s either disarmingly modest or just a bit crap. Either way, it’s British through and through.

      If—and, frankly, it’s a bloody big if—we accept British pre-eminence in modern mapping owing to the adoption of the Greenwich Meridian as the gold standard for measuring lines on a map, then one event gave birth to this certainty. That was the creation of an earlier imaginary line on the landscape, the first precisely calibrated base line across a stretch of English countryside, from which all initial triangulations were taken to produce what soon became the Ordnance Survey. It took place in the summer of 1784, and for reasons that are also gloriously British: once again, a fierce spirit of one-upmanship against the French and a supremely thin-skinned paranoia that they were insulting us.

      We had a lot of making up to do; by the late eighteenth century, French map-making was leagues ahead of that of its clod-hopping British cousin. Nearly a century earlier, their experiments in establishing accurate lines of longitude and latitude had proved that the world was an oblate spheroid, rather than a perfect sphere, which had tremendous impact on the precise measurement of relative distances, radically altering the shape and size of France itself as presented on a map. Coupled with advances in triangulation and surveying, the Académie Royale produced, in 1789, by far the finest and most ambitious cartography that had ever been made of one country: a complete set of 180 maps, covering all of France, at a scale of 1:86 400, just under one and a half miles to the inch. Even the detail on the maps was starkly different: while we were still delineating our upland areas with crude shading or lumpy molehills scattered over the landscape, the French were developing sophisticated systems of hachures—groups of parallel lines to indicate height—before pioneering the use of contour lines on some maps from the 1750s.

      The year 1789 is better remembered in France for rather bloodier reasons than the publication of the national map, the Carte de Cassini as it became known, after César-François Cassini de Thury, the Director of the Paris Observatory and its principal progenitor, who had died of smallpox in 1784, leaving his son to continue the work. The new revolutionary government looked with grave suspicion on anything royale, the Académie included, although they were more than delighted with the maps and promptly took over all responsibility for their production and publication. The Académie Royale was closed down (to resurface a few years later as the more egalitarian Académie des Sciences), Cassini junior was imprisoned, while Académie director Antoine Lavoisier was carted off to the guillotine. It was at just this moment in history that the British were starting to get their act together, and, aided by the chaos in France, were soon able to outstrip their neighbours. Though, as ever, it took some pompous prodding by the French to sharpen us up.

      That came six years before the Revolution, in the shape of a missive from Cassini de Thury to King George III, in which he loftily pointed out that the world’s two principal meridians, those of Paris and London, were out of kilter in both longitude and latitude. His inference was that, thanks to the superior surveying and triangulation of the French, the mistake was almost certainly on our side of the Channel, and would His Majesty care do something about it? He further rubbed salt into the wounds by pointing out that he himself had checked the trigonometry on the French side all the way up to the Channel coast, and, using a telescope, had established many landmarks on the English side that could be useful if we could be bothered to do a proper survey. The King’s principal Secretary of State, Charles James Fox, passed on the letter to Sir Joseph Banks, President of the Royal Society in London. Many of its members were outraged by the slurs it contained, the Astronomer Royal, the Reverend Doctor Nevil Maskelyne, firing off a hasty rebuttal of the French claims. But there was one Fellow of the Royal Society who received the news with equanimity, bordering on glee, for he knew that this was the chance for which he had been waiting for decades.

      We know frustratingly little about Major-General William Roy (1726-90), a map addict of impeccable credentials and the father of the Ordnance Survey. No portrait survives of him, few biographical details have come our way, but, from his plans, letters and publications, we can see a man utterly driven by maps and an insatiable urge to make them ever better. He started in his native Scotland, working with the surveying crews that had been drafted in as a response to the Jacobite uprisings in the Highlands of the 1740s. The official response was the same as always: go deep into enemy turf, build roads and military outposts, move the population to where they could better be tracked, and, most importantly of all, comprehensively map it. For years, this was Roy’s day job, though, as a sideline, he also worked obsessively to map the Roman remains of Scotland, for they had employed much the same techniques in suppressing the clans fifteen centuries earlier. There’s not much doubting what his specialist subject would have been on Georgian Mastermind.

      The first survey of Scotland, between 1747