Don't blame Hadrian for Bush's wall.

President Bush has a strange enthusiasm for walls (strange, because that mother of walls in Berlin isn’t exactly regarded as a stunning success). He would like to put, if not a wall, then at least a barbed wire fence along the almost 3,500 kilometer frontier between the USA and Mexico. And, unless Nouri al-Maliki manages to put the brakes on, there will soon be concrete walls between Sunni and Shia areas of Baghdad, to keep car-bombers out (or in).

Bush isn’t the only one, of course. Israel is busy constructing its West Bank barrier, parts of which are 8 meters high, in concrete. Less well known is a wall put up in Padua in north Italy, as a “crime fighting measure”, around the high-rise Anelli estate. In fact the Guardian last week came up with almost thirty modern security walls, either built or under construction. One, the electric fence between South Africa and Mozambique has apparently killed more people than were killed trying to cross the Berlin Wall.

The Great Wall of China may be one ancestor here. But the usual western approach is to point the finger back, way beyond Berlin, to the emperor Hadrian. Regret these awful barriers though we do, is the line, there is a fine classical precedent in the second century AD with Hadrian’s attempt to keep the nasty barbarians out of the Roman empire. That is, “Hadrian’s Wall”.

Another misuse of the classical past I’m afraid.

Sure, the popular image of Hadrian’s Wall is just that: cold, wet, Roman squaddies constantly patrolling the bastions, and periodically attacked by the native hordes trying to penetrate the homeland – unsuccessfully, of course, as the Wall was such an effective barrier.

It can’t, in fact, have been anything like that, and archaeologists have been debating for decades exactly what Hadrian’s Wall was for. The one relevant reference in classical literature (“he was the first to build a wall to separate Romans and barbarians”) may look as if it supports the popular line. But it’s written by a flagrantly unreliable late Roman biographer of Hadrian, who probably had no better idea than we do of what was going on in the second century AD.

And there are all kinds of problems with that approach. For a start, the Wall isn’t anything like as powerful a defensive line as we tend to imagine. There are one or two spots where it looks very impressive (and those are where the publicity photos are usually taken). But when it was first built most of the western part was not that great masonry structure, but a simple turf rampart, which wouldn’t have deterred most self-respecting barbarians. Besides there are an improbably large number of gates (80) for a serious defensive barrier.

Some modern archaeologists think that we are dealing with a mechanism of surveillance,  or with a means to control movement between territories rather than an attempt to prevent incursions (maybe there was a cash levy on goods crossing the line . . .?). Others think that it was more a way of establishing a line of communications from East to West, rather than blocking invasions from the North. Still others think that the main purpose was symbolic: Hadrian was one of those unwarlike Roman emperors, who needed some military street-cred; what better than a few miles of military masonry in the rugged province of Britannia?

But the bottom line is the way the Romans generally thought about frontiers and frontier regions. Despite the impression given by Hadrian’s Wall (and by a few other places largely in Germany) that they saw a linear divide between the empire and the barbarian world, the Roman image of the frontier was usually much more subtly nuanced. The empire shaded into “foreign” territory across many kilometres that were melting pot of cultural difference and often a hot-spot of trading and commercial activity. It was a question of frontier zones, rather than frontiers – governed partly by Rome, partly by a whole variety of non-Roman powers. Hadrian’s Wall, whatever its function, was an exception.

President Bush and our other wall-crazy political leaders might learn from that.