In 1984 a German scholar worked out that 210 reasons had been advocated for the fall of the Roman empire in the West in the fifth century AD - from bureaucracy to deforestation, from moral decline to over-hot public baths, from female emancipation to gout. But they can't all be right and in his fine narrative history, combining story-telling with a vivid use of original sources, Peter Heather makes a strong case for one overriding explanation: the Huns.

Meanwhile, Bryan Ward-Perkins [The Fall of Rome and the End of Civilization, Oxford, £16.99, 256 pp] poses a different question: what were the implications of the end of the empire for your average provincial? Are we talking of a broadly seamless transition from centralised Roman control via local barbarian kingdoms to the medieval world, or something rather less comfortable?

Heather sets the scene in the early fourth century AD. The Roman army was still the most ruthlessly proficient in the world, and it had to be: frontiers needed guarding. To finance it, a vastly increased bureaucracy was in place. The provinces - stretching from Hadrian's Wall to Iraq, from the Rhine to the Atlas Mountains - were now thoroughly Romanised and demanding a say in imperial politics. A single emperor simply could not handle the workload. So in 295 Diocletian created a system of emperors and sub-emperors.

One important result of all this was that decisions were now taken in the great imperial palaces that sprang up all over the empire (Ravenna, Trier, Split, Constantinople, etc). The city of Rome was too far from the action. The Senate still met there, but was a shadow of its former self.

As for the barbarians (the northern Germanic tribes stretching from the Rhine to the Black Sea), they had nothing to offer Rome and after the destruction of Varus' legions in AD 9 were no longer thought worth taking on. They still raided from time to time, and Romans were not averse to doing deals (Germans made excellent soldiers). But the tribes were too disunited to pose a serious threat.

Edward Gibbon argued that this world was inherently unstable, doomed to collapse. Heather disagrees. Multiple emperors, admittedly, did cause sporadic and dangerous civil wars. But the problems generated by, for example, slow communications over massive distances, rigid economies and reactive bureaucracies were not new; tax increases to pay for the military did not lead to revolt, since provincials still saw benefits outweighing disadvantages; nor did Rome's Eastern (or "Byzantine") empire collapse - indeed, in the sixth century it fought back in the West under the emperor Justinian; and so on.

According to Heather, the collapse in the West was triggered in summer 376 by one event with huge ramifications: the sudden and quite unexpected irruption of a new and terrifying people into barbarian territory on Roman borders - the Huns. It was pressure from them that drove barbarians (Goths, Visigoths, Franks, Alans) into the Western empire over the next 60 years. The Romans were helpless to stop them.

The result was the establishment within the empire of barbarian kingdoms from Gaul to Spain, from Italy to North Africa. As its tax revenue dried up, Rome lost the capacity to raise troops to force these kingdoms back into the imperial fold. Stripped of the power to compel, it was thereby stripped of its authority. Local élites, so supportive of Rome when Rome could support them back, saw that their only option now was to collude with their new masters, whose forced migration had had the effect of forging them into cohesive barbarian "supergroups" capable of establishing permanent kingdoms that were to form the basis of modern Europe. In 476 the last Roman emperor, called (ironically) Romulus Augustulus ("little Augustus"), was quietly pensioned off by the barbarian Odoacer, and that was that.

Enter Ward-Perkins, laying about himself in fine, combative style. He agrees that many barbarians wanted not to destroy the empire but to settle securely within it; that the Romans were often happy to accommodate them (though some locals saw this as "selling out"); and that the new barbarian kingdoms frequently maintained the local Roman way of doing things - which had, after all, worked for hundreds of years.

Ward-Perkins's "but" is based on a mass of closely interpreted archaeological evidence. Setting his face firmly against scholarly fashion, which dictates that everything about "Europe" must be "positive" and that no cultures are allowed to be more sophisticated than others, he argues that the demise of Rome led to a collapse of general living standards from the 5th to the 7th centuries so severe that the result was effectively "the end of civilisation".

Because Rome's complex and highly developed economic, social, military and cultural infrastructure folded with the empire, a huge range of material goods, taken for granted across the whole Roman world by rich and poor alike, could no longer be produced, let alone delivered. No more fine pottery in massive quantities from far-off places for any who wanted it; little by way of coinage, or brick, tile and stone building (and what there was, like churches, much smaller than before); luxury goods only for the few, and these locally produced; agricultural productivity in decline; severely restricted levels of literacy (no more of those Pompeian walls covered in graffiti); insecurity the norm. Simplicity was the order of the day and the effects were felt from peasants to kings. It took centuries to get things back to where they had once been.

There is nothing mealy-mouthed about this hard-hitting and beautifully written assessment which, I am delighted to say, will cause a great deal of trouble. Between them, these two Oxford dons have created stimulating new beginnings to thinking about the end of the Roman empire in the West.