In her book Under Another Sky the Guardian’s chief arts writer CHARLOTTE HIGGINS examines the impact of the Romans on Britain’s history, landscape and imagination. Next month she will be at the Harrogate History Festival to discuss the legacy of the Romans with Dr Richard Hobbs of the British Museum.This extract from her book is taken from the chapter on York

“NO city or town, in the united kingdoms, can present to the Author so great a variety of wonderful events, for enriching the page of history; or exhibit to the Antiquary so many mouldering relics of former ages, as York, the ancient and venerable capital of the North.”

SO began W. M. Hargrove’s 1818 History and Description of the Ancient City of York. Notwithstanding Hargrove’s hyperbole, it is quite true that the later history of York is inextricably bound up with its origins as Roman Eboracum. The archbishopric here (the primate still signs himself ‘Ebor’) sprang up because of York’s past as a great Roman centre.

York was the springboard of invasion, the base of operations for the legions as they advanced to Hadrian’s Wall and beyond. When the province of Britain was split into two administrative chunks in the third century, the city became the capital of the northern portion, Britannia Inferior, or Lower Britain. The first fortress was established in AD 71 as the troops marched their way towards Caledonian conquest.

The emperor Septimius Severus settled his imperial court here between AD 208 and 211 while he and his sons, Caracalla and Geta, waged war against the northern tribes of the Caledonians and Maeatae. A century later, in 306, the commander Constantius Chlorus died here; and it was in this city that his son, Constantine the Great, was acclaimed emperor by the legions.

Six years afterwards, Constantine would change the destiny of the empire by converting to Christianity at the Battle of the Milvian Bridge, outside Rome. There are indeed moments when York has been cast on to the great stage of world affairs.

When archaeologists were brought in to dig beneath the mighty Norman heights of York Minster in 1969, their aim was to discover the Anglo-Saxon church that the Venerable Bede had described as being the site of the baptism of King Edwyn of Northumbria in 627.

What they actually found was a corner of the Roman principia, or fort headquarters, the elaborately frescoed walls of which are now displayed in situ in the minster’s undercroft. Also here was a roughly bullish sculpted head that may, or may not, have been meant to represent Constantine the Great himself.

By way of Christian aetiology for the spot, the minster authorities had to make do with a rather grubby terracotta tile fragment with XP – chi-rho, the first two letters of ‘Christ’ in Greek lettering – very faintly marked on it. This too is on show, with some flourish, its label making the suggestion that late Roman York had a ‘considerable Christian community’. (In fact there are only the faintest traces of Christianity in the archaeology of Roman York, though the city is known to have sent a bishop to the Council of Arles in 314.)

As I wandered through the dark spaces under the minster, it seemed to me that there was something appropriate in the Roman fortress’s having asserted itself in this way, beneath the soaring spaces of York’s most famous monument. The Norman minster, and no doubt its elusive Anglo-Saxon predecessor, were built here precisely because the fort headquarters represented the ancient seat of power. This was a potent spot; the place from which authority had to be wrested away and repurposed for a new Christian age.

There is a beautifully preserved eighth-century Anglo-Saxon helmet in the Yorkshire Museum, which was found by a JCB operator in the city in 1982. The inscription that runs along the metal band on its crest tells us that its owner was Oshere, and that he was a Christian. The words themselves are in Latin – as if Oshere was borrowing the old rulers’ power, as well as their language.

• This is an extract from Under Another Sky by Charlotte Higgins published in paperback by Vintage at £9.99.

• Charlotte will be in Harrogate for the Harrogate History Festival in the Old Swan Hotel on October 25 to discuss the impact of the Romans on Britain’s history and landscape with Dr Richard Hobbs, curator of Romano-British collections at the British Museum. Charlotte Higgins and Richard Hobbs, Harrogate History Festival, Saturday, October 25, 2pm. Tickets £11.

For tickets, and to find out about other events at the festival, visit www.harrogateinternationalfestivals.com