Bishop's Hatfield & Knebworth in Hertfordshire. Hatfield, originally Bishop's Hatfield, is a town in the Welwyn Hatfield district of Hertfordshire, in the south of England. St. Albans was the first major town on the old Roman road Watling Street for travellers heading north and was previously the Roman city of Verulamium. After the Roman withdrawal, and prior to becoming known as St. Albans, the town was called Verlamchester or Wæclingacaester.

The St. Albans area has a long history of settlement in southern Hertfordshire. The Celtic-Belgic Catuvellauni tribe of southeastern Britain had a settlement at Prae Hill a mile or so to the west from the Gaul region of Châlons-en-Champagne. They appear as one of the civitates of Roman Britain in Ptolemy's Geography in the 2nd century, occupying modern Hertfordshire, Bedfordshire and southern Cambridgeshire and based around the town of Verulamium (modern St. Albans). The Roman town of Verulamium, second-largest town in Roman Britain after Londinium, was built alongside this in the valley of the River Ver a little nearer to the present town centre.

North of the Thames and to the west of the Trinovantes, corresponds to that later occupied by Cassivellaunus and the Catuvellauni from Julius Caesar's first expedition to Britain in 54 BC. The mediaeval town grew up on the hill to the east of this around Benedictine St. Albans Abbey. This at the spot where tradition has it that St Alban, the first British Christian martyr, was beheaded sometime before AD 324. It was, at one time, the principal abbey in England and the first draft of Magna Carta was drawn up there, reflecting its political importance.

Dio tells us that by this stage Cunobelinus was dead, and Togodumnus and Caratacus led the initial resistance to the invasion in Kent. They were defeated by Plautius in two crucial battles on the rivers Medway (see Battle of the Medway) and Thames. He also tells us that the Bodunni, a tribe or kingdom who were tributary to the Catuvellauni, switched sides. This may be a misspelling of the Dobunni, who lived in Gloucestershire, and may give an indication of how far Catuvellaunian power extended. Togodumnus died shortly after the battle on the Thames. Plautius halted and sent word for the emperor to join him, and Claudius led the final advance to Camulodunum. The territories of the Catuvellauni became the nucleus of the new Roman province.

The site of Verulamium is mostly in Verulamium Park, south of St. Albans Cathedral and the River Ver. The longest surviving stretch of the city wall is found on the east side of the city, together with the foundation of the London Gate. A small piece of the wall on the north side, "St. Germain's Block" may have been preserved as part of a medieval chapel to St. Germain. The wall was built in 265-270 from mortared flint layered with red brick bonding.
The Abbey Church (formally the Cathedral & Abbey Church of St Alban but still known locally as The Abbey) became the parish church when it was bought by the local people at the dissolution of the monasteries. The growth of St. Albans was generally slow before the 20th century, reflecting its status as a rural market town, a pilgrimage site, and the first overnight coaching stop of the route to and from London - a fact which also accounts for its many inns, many dating from Tudor times.

Verulamium gained the status of municipium ca 50, allowing its leading magistrates to become Roman citizens. Caratacus, however, had survived, and continued to lead the resistance to the invaders. We next hear of him in Tacitus's Annals, leading the Silures and Ordovices in what is now Wales against the Roman governor Publius Ostorius Scapula. Ostorius defeated him in a set-piece battle somewhere in Ordovician territory (Battle of Caer Caradoc) in AD 51, capturing members of his family, but Caratacus again escaped. He fled north to the Brigantes, but their queen, Cartimandua, was loyal to the Romans and handed him over in chains. Caratacus was exhibited as a war-prize as part of a triumphal parade in Rome. He was allowed to make a speech to the Senate, and made such an impression that he and his family were freed and allowed to live in peace in Rome.