All these markets were at places that had no need of names before, and a rain of new place names was falling across Dane-controlled England from Lunden to Eoforwic and beyond – and most of those names were Danish.

Arngrim didn't like this. 'Even if Alfred wins,' he growled, 'even if he or his sons push the Danes all the way back into the sea where they came from, it will be hard to scrub all this out of men's minds.'

At last they reached Eoforwic, which the Romans had called Eburacum, and its new Danish kings called Jorvik. Whatever its name, the stony Roman core of the city still stood square on its high ground over the river. Wharves snaked down to the water, and carts and foot-travellers slogged up rough tracks to the city walls.

To reach the city the travellers had to cross a bridge, Roman-built, decayed, eroded, scarred by fire, but still solid, and busy with travellers. From the bridge Cynewulf peered down at a crowded waterway. Danish ships made their way with oars plashing, sails furled, and masts lowered so they could make it under the bridge. But there were lesser vessels too: log-ships each carved out of a single tree-trunk, and boats that were little more than leather-covered frames, like the currachs that had once carried the Irish monks into the ocean. These smaller craft, piled high with fish, eels and dried bundles of reeds, were manned by English folk whose ancestors had made their living from the river for generations before the Danes.

Once they were over the bridge they followed a good road that ran up from the river bank, through a jumble of slumped wooden buildings, straight to a gatehouse in the solid Roman walls. After centuries of weather and war the walls were much repaired, but they still stood twice as tall as a man. In one corner a tower had been erected, much cruder than the original Roman structures, perhaps planted there by a long-dead Northumbrian king. Leofgar said that for a while the Danes had installed a puppet English king here, but now Danish kings had taken over, and the latest ruler was planning a proper palace, a timber marvel to be built in the south-east corner of the walls.

At the gatehouse they were stopped by tough-looking Danish warriors who demanded a toll. Once Arngrim had paid up Leofgar led them all confidently into the town.

Inside the walls the place felt even more cramped than Cynewulf had expected, full of low wooden buildings crammed in around the feet of the vaster Roman ruins. He was overwhelmed by the crowds, the yells of vendors, and above all by the stink, of human sewage and rotting thatch and animal droppings. It was like walking into a vast compost heap. But this crowded place was full of life, and Cynewulf, unused to cities, felt excitement stir in his soul.

The people dressed brightly, in tunics and leggings dyed yellow, red, black and blue. They wore cloaks against the winter cold, but the men kept them thrown back so one side of their bodies was always exposed, and they all carried at least one weapon, a sword, axe or knife. They were tall, well-muscled, intimidating – and you couldn't tell at a glance who was Danish and who English.

If the people were impressive, their homes were less so. Built on rough timber frames, they were roofed by ragged straw or turf, and their walls were of woven hazel or willow packed with mud or dung. The Danish occupation of Jorvik was only a dozen years old, so none of these huts was older than that – and yet, pounded by northern rains, their misshapen hulls were already slumping into the filthy earth.

The amount of trade going on was astounding. The houses were built long and thin, crowding each other for frontage on the main streets. In the workshops behind these frontages tanners scraped and cobblers hammered, potters turned their wheels, and weavers treadled their looms with threads of wool weighted by pierced discs of fired clay. Leofgar the weapons dealer was on friendly terms with many of the smiths. In the houses open fronts wares of all sorts were displayed, from pottery and wooden tableware and jewellery to broiled rats sold to children for a clip from a silver coin. Outside the carpenters' shops cups and plates were heaped up, wheel-turned from blocks of ash, dozens of them all but identical to each other, remarkable if you were used to hand-made goods. Cynewulf was very struck by one store that sold nothing but shoes, sewn from leather or moleskin, racked up on shelf after shelf like roosting birds.

Ibn Zuhr fingered a pottery jug, deep crimson, symmetrical, well finished. He ignored the Danish jabber of the man who was trying to sell it to him. 'Look at this. I haven't seen anything of this quality since I was taken from Iberia. And I would guess that this is the first genuine city, as a Greek or a Moor would understand it, to be functioning in Britain since the Caesars. All in a decade!' Ibn Zuhr seemed fascinated, in his cold, supercilious way. 'The Danes, you know, have trading links from Ireland to the Baltic, from Greenland to Iberia. Under them, trade is booming, within the country as well as beyond.'

'The Danish trade can boom all it likes,' growled Arngrim, 'until Alfred comes here and lops off its head like a weed. And then we'll get back to the old ways.'

Ibn Zuhr the slave could only agree with his master.

Leofgar led the party to the city's heart, where the shells of many Roman buildings still stood. It was quiet here, away from the bustle of the Danish markets. Cynewulf curiously walked inside the immense walls of what Leofgar called the principia, once the headquarters of a Roman legion, a mighty structure that could still be seen for miles around. Though now its roof had collapsed, leaving heaps of smashed tiles, the principia had stood, without maintenance, for four hundred years. Leofgar said that the Emperor Constantine had been elevated to the purple in this very building, accompanied by lightning strikes, flights of birds, crosses in the sky and other miracles. Cynewulf was a natural sceptic, and found it very hard to believe that the mightiest emperor of them all could have had anything much to do with Britain – and certainly not Northumbria, this dismal corner. But Leofgar seemed to enjoy the fantasy. Now the ground was being cleared of its paving stones, and bodies planted in the exposed earth. Thus a Roman principia was being turned into a pagan cemetery.

Near the south-western corner of the principia, Cynewulf found a small stone-built chapel. This was actually a famous church, if you knew any Northumbrian history, built on the site of a wooden chapel set up here by King Edwin on the occasion of his conversion two centuries before. It was crudely built, and looked like a toy set beside the tremendous wall of the Roman ruin. But, neatly laid out on an east-to-west axis unlike the principia, it was unmistakably Christian. And where the principia was doomed to decay and demolition this small chapel was surely the seed of grander minsters to rise up in the future.

The little church was just too tempting. Overwhelmed by his journey and all he had seen, Cynewulf begged leave of his companions and went inside to pray.