Amid all the modern talk of a possible future United States of Europe, complete with a common currency, it is easy to forget that what is now Oxfordshire was for centuries a part of just such a super state.

In fact, the Roman super state stretched well beyond the confines of modern Europe. This point was brought home to me dramatically not long ago when, sitting in bright sun on a lonely beach in North Africa I came across a mosaic just beneath the surface of the sand. My thoughts flew back to Widford, to the little Anglo-Saxon chapel near Swinbrook, in West Oxfordshire, where some years ago a mosaic was exposed beneath the floor of the chancel – the chapel having been built on the site of a villa.

I remember it particularly because the wife of the vicar had placed an old-fashioned bar heater on it, the chapel’s only heating appliance.

For about 500 years, Britain was effectively part of the Roman world, and for about 350 of those years it was a province directly under Roman rule. To put that in some sort of context, Henry VIII came to the throne 500 years ago, the Sheldonian Theatre at the heart of Oxford had not yet been built 350 years ago, and British rule in India lasted barely two centuries.

As every schoolboy knows, Julius Caesar visited Britain in 55 and 54 BC (Veni, Vidi, Vici; I came, I saw, I conquered). But in fact this unruly island, full of fighting tribes, was not formally annexed to Rome until the conquest of AD43.

From the start Oxfordshire prospered. True, it did not yet exist as an administrative entity in its own right but leaders of the three tribes, or civitas, that controlled it were quick to embrace the benefits of Roman civilisation.

These three tribes were the Catavellauni in the east, with their capital at Verulamium (now the city of St Albans); the Artebates of Silchester in the south; and the Dobunni of Corinium (Cirencester) in the west.

As early as AD47, the Romans consolidated their rule of the future Oxfordshire by building Akeman Street right through it – vaguely along the line of the A41 – from St Albans to Cirencester, and a south-north road from Silchester to Watling Street in Northamptonshire. Along these roads, towns were developed, notably Dorchester and Alchester (now Bicester).

But the most noticeable traces of the peaceful, cultured, and civilised rural way of life that Romanised Britons in Oxfordshire enjoyed are to be found in the remains of their villas, particularly the biggest and best preserved of them at North Leigh.

It is clear that the people who lived here knew all about how to make themselves comfortable. The lovely mosaic still on view there was made by the school of mosaicists in Cirencester, then there were elaborate bath and hypercaust heating arrangements, not to mention large quantities of wine either grown on the banks of the River Evenlode or imported from warmer parts of the empire.

Much of the money to pay for such luxury came from Cotswold wool which was used to make the Birrus Britannicus, a sort of hooded outfit worn throughout the northern empire.

Sadly, Oxfordsire's best mosaic, at Stonesfield villa, was destroyed in the 18th century by a farmer fed up with scholars tramping across his crops to look at it. Aptly enough, it portrayed Bacchus, God of the Good Life, riding a lion. Fortunately, a copy survived in the form of a carpet.