The fact that Celtic nations survived down to the present is no mean feat considering the waves of invaders ancient Britain faced from the Romans to the Normans. They also faced sickness, famine, and slavery. Not only did they face physical annihilation, but the Celtic Gods were also being replaced or syncretised with foreign deities.

Roman Britain, 43 – 410 AD

The Romans had no reason to invade Britain in 43 AD. Their empire already extended from the Channel coast to the Caucasus, from the northern Rhineland to the Sahara. After three legions were destroyed in the Battle of the Teutoburg Forest by German tribesmen in 9 AD, the emperor Augustus concluded that the empire was overextended and called a halt to new wars of conquest.

The invasion of Britain was a war of prestige. After emperor Caligula had been assassinated in 41 AD, Claudius took the throne. Claudius was an unpopular choice by many, including the Senate. Claudius used Britain as a quick political fix to secure his position. Future historians may conclude that certain political leaders manufacture wars in our time for the same purpose.

A century before, in both 55 and 54 BC, Julius Caesar had invaded Britain with the aim of conquest. But revolt in Gaul (modern-day France) had drawn him away before he had beaten down determined resistance from our Celtic ancestors.

In the popular Roman imagination, ancient Britain was a place of marsh and forest, mist and drizzle, inhabited by ferocious blue-painted warriors. Conquering a place where Caesar had failed would strengthen Claudius’ reputation with the senate.

An army of 40,000 professional soldiers – half citizen-legionaries, half auxiliaries recruited on the wilder fringes of the empire (including Persia) were landed in Britain under the command of Aulus Plautius.

They landed in the area Richborough in Kent, Chichester in Sussex, or perhaps both. They fought a great battle with the south eastern Catuvellauni tribe and defeated them, possibly on the River Medway. Then, in the presence of Claudius himself, they stormed the enemy capital at Camulodunum (Colchester). They created a huge fort in the same area that Colchester Castle was later built.

Pushing into the south west of Britain, the Romans fought a war of sieges to reduce the great Iron Age hill forts of the western Celtic tribes. They continued through and beyond the Midlands, but encountered stiffening opposition as they approached Wales, where the fugitive Catuvellaunian prince, Caratacus, rallied the Welsh tribes on a new anti-Roman front.

Whilst Wales took decades to subjugate, there was revolt in Norfolk. Following the death of her husband and co-ruler, the 
Romans not only failed to recognise the position of Queen  Boudicca of the Iceni, but her daughters were raped in front of her. Between 60-61 AD, bitterness against Roman oppression drove the Celts into a revolt that came close to expelling the invaders. The Celts burned Camulodunum to the ground and later attacked Londinium (London).

Caractacus (who was now King) went to the largest tribe of the Celts, the Brigantes, for assistance but was betrayed and handed over to the Romans by the treacherous Queen Cartimandua and spent the rest of his days in exile in Rome.

Under Governor Agricola, the Romans occupied northern Britain, reaching the Moray Firth in 84 AD. This was as far as the Roman Empire extended in Britain.

The empire’s frontiers were under attack and legion numbers in Britain had to be reduced. A gradual withdrawal was carried out from the far north, eventually bringing the army to a line that stretched across modern Northumberland from Newcastle-upon-Tyne to Carlisle on the Solway. Hadrian’s Wall was constructed in 120s and 130s AD to protect the Roman Empire by attacks from the Picts (Scottish lowlands tribes).

The rest of the Roman army was stationed in the west and the north – in lonely auxiliary forts in the Welsh mountains, the Pennines, or the Southern Uplands of modern Scotland; or in one of the big three legionary fortresses at Isca Silurium (Caerleon), Deva (Chester) and Eboracum (York).

Throughout 350 years of Roman occupation, the army dominated the Celts. Settlements of craftsmen and traders grew up around the forts, sustained by army contracts and soldiers’ pay. Local farms supplied grain, meat, leather, wool, beer, and other essentials. The Celtic land was impoverished and sparsely populated. The Roman army took what little surplus there was, so there were few of the trappings of Romanised life experienced in Italy.

It was only in the lowland zone – south and east of a rough line from Lincoln to Exeter – where parts of Britain began to look distinctly Mediterranean. In this region, Iron Age tribal centres were redesigned as Roman towns, with regular street-grids, forums (market squares), basilicas (assembly rooms), temples, theatres, bathhouses, amphitheatres, shopping malls and hotels.

Although the models of town planning and public architecture were Roman, the people in charge were not. The towns were built by local gentry, who, in the space of a generation or two, converted themselves from Celtic warriors and Druids to Romanised gentlemen.

The upper classes in Southern Britain had found a new lifestyle. Blue paint and chariots were gone, to be replaced with Gaulish wine and Greek mythology and philosophy. The Romans were heavily influenced by the Greek philosophers of the day, and their Gods were often versions of the Greek Gods. For instance, Heracles became Hercules.

For the rulers of the Roman empire, changing the culture of conquered elites was good politics. The empire was ruled from the towns, where councils formed of local gentry were responsible for tax-collection and keeping order in the surrounding countryside. It was government by delegation, but it was highly successful and still a template used by local and central government today.

Instead of an influx of foreign overlords stirring up resentment, the native elite ran things on Rome’s behalf. And in gratitude for having their power and property preserved, they proved loyal servants. The evidence is in the enthusiasm with which they Romanised.

Most of the twenty or so Roman towns had a full set of public buildings by the mid-second century AD. Already, many of the gentry had started building town houses and country villas. From this time onwards, there was a full-scale housing boom at the top end of the market.

Large towns like Verulamium (St Albans) and Corinium (Cirencester) soon had fifty or more grand houses and dozens of villas within a day’s ride of the centre. Companies of mosaic layers, fresco painters and potters sprang up to feed the boom in luxury living, and the shipping lanes, rivers and roads were busy bringing in such specialities as fish sauce from Spain, Rhineland glassware, and Pompeian bronzes.

Rome’s days were numbered. Financially, they had overspent and were overstretched. Their army ‘lived off the land’ as it marched across the empire. Rome’s quarter of a million strong army was proving difficult to pay and sustain. Rome’s enemies were getting stronger, especially the Germans and Goths of Central Europe, who threatened the Rhine and Danube frontiers.

By the mid-third century AD, the Roman Empire was in decline, and their resources were ploughed into defence. Walls were built around the towns, turning them into fortresses. Public buildings were boarded up, and old mansions crumbled and became overgrown with weeds.

The Roman emperors of the later empire were more dictatorial and ruthless (and despised), aiming to centralise and streamline administration and to force people into supporting the defence effort.

Embracing Christianity was part of this programme – evidenced in Britain by a handful of late Roman churches found in excavation, some mosaics with Christian images, an occasional silver spoon or cup inscribed with Christian motifs.

Society became apathetic, civic spirit dwindled, the towns continued to decline, and even the villas eventually succumbed. Britain was repeatedly raided – by Anglo-Saxons in the south east, Irish in the west, and Picts in the north. New coastal forts were built to meet the threat, but the troops were stretched too thin to hold the line for long.

Then, when Italy itself was attacked, some troops were withdrawn from Britain altogether to defend the homeland.

No clear decision to ‘decolonise’ Britain was made. The garrison was run down over a generation, and then the remnant was simply cast adrift to fend for itself. Army pay (represented by finds of Roman coins) ceased to arrive. The remaining soldiers became part of Celtic Society, drifting off to make a living as outlaws, mercenaries, or farm labourers.

By about 425 AD at the latest, Britain had ceased to be in any sense ‘Roman’. Towns and villas had been abandoned, the only pottery was homemade, barter had replaced money, and the mosaic and fresco workshops had all closed.

Britain had entered a new Celtic age outside the empire, apart from the continent, an age without Roman tax collectors and landlords.