STEPHEN LEWIS loves a book about the city's darkest age.

York in the year AD 500 wasn't a very nice place. It was a post-apocalyptic nightmare, in fact - the city ruined and abandoned, the land around occupied by encampments of blood-daubed, superstitious savages.

There is a tantalising glimpse of it in historian Simon Young's brilliant new book, AD 500 - a kind of fictionalised travel guide to Dark Age Britain.

Simon imagines a party of Greeks from Byzantium - centre of the civilised world - travelling through the former Roman province of Britain.

They are appalled by what they find. York, the city of Constantine, is crumbling and empty, occupied only by ghosts and shadows.

Saxon tribes, having driven out the Romano-British people, have left it to decay and set up their own rough new camps throughout the Vale of York.

"The prudent traveller will... try to still his rage when he sees how they (the Saxons) have reduced the ancient, mortared heart of the north (York), letting it collapse into ruin," writes Simon's Greek narrator.

Worse is to come. The most powerful of the northern Saxon warlords has set up his headquarters east of York, at the river Derwent. His tribal HQ is a place of superstition and bloody human sacrifice. "There... the traveller will discover the torn limbs of men and beasts swinging from the trees of a glade," Simon's narrator reports.

It's a scene straight out of Apocalypse Now - or out of Heart of Darkness, the Joseph Conrad novel on which the film is based.

Was it really like that? Yes, says Simon, a Cambridge-educated historian and author who has spent ten years researching his book.

By AD 500, it was already almost a hundred years since the Romans had abandoned Britain, leaving behind them a defenceless Romano-British people grown soft through civilisation.

It was the nearest thing to an apocalypse Europe has ever seen, Simon says. A kind of Roman Britain version of Mad Max.

As the Romans left, the great cities such as York were abandoned. Law and order had gone, and civil collapse meant there were no jobs, no food, none of the infrastructure needed to support a city.

The abandoned people, who a few years earlier had had piped water and had sent their children to school, had no choice but to take to the land, trying to learn, inexpertly, how to farm.

At first, a few families may have tried to defend their homes, Simon says. "People gave up most of the cities, but defended bits they could defend." Some, in a desperate attempt not to evacuate their cities altogether, even spread earth across the city centre to try to grow crops there, Simon says.

It couldn't last - especially once the barbaric Saxon tribes of Germany realised how defenceless Britain was. They invaded, sweeping across the country like a dark tide, and driving the surviving Britons into Wales and Cornwall.

There's a great account of how it might have happened in Simon's book, quoted by his Greek narrator from a Romano-British historian.

"The arson fed by the hands of the dreadful Saxon grew and grew and ran across the island until the blaze reached from sea to sea," it goes. "This fire spared nothing, neither town nor farm. All the ancient cities were undone and entered by smashing rams, the inhabitants then cut down by blades - burghers, councillors and priests alike - while by the light of the fires weapons glinted."

By AD 500 it was all history: the British driven out of England, except for enclaves of civilisation in places like London and St Albans, besieged behind their great walls - and the Saxon warlords scrapping amongst themselves for what was left.

It sounds grim: but Simon's book is very funny. His Greek travellers' journey takes them from one end of the country to the other - and even to Ireland - and he's had a ball capturing their snooty, supercilious tone.

They certainly encounter some strange sights - Irish men sucking each-other's nipples instead of shaking hands as a sign of friendship and alliance, beaver testicles being used as medicine and entertainment from professional farters.

A.D. 500: A Journey Through The Dark Isles Of Britain, by Simon Young is published by Weidenfeld & Nicolson, £14.99

Updated: 08:59 Saturday, April 16, 2005