The Romans conquered Britain in much the same way they overcame the Celts in Gaul. They would build alliances with various tribes through a variety of means. One way was the client-ruler style. In this relationship, which was personal and and special, and was dissolved upon the death of the client, the Romans would set up a series of treaties, taxes, and other items. The clients would then be provided protection by the Roman legions in Britain from the other tribes. Upon the death of the special client, the relationship was put up for review and reassesment by the Romans. One of the British tribes that had such a relatioanship were the ICENI.
Prasutagus was the client-king of the Iceni, whose center of power was around Norfolk, in modern England. When he died in 61 AD, the Roman emperor Nero's representative Decanius Catus moved with incredible haste to do an inventory of the property of the Iceni and their late king., Prasutagus had left a will in which he left half of the property to the emperor, and the other half to his two daughters. The Romans declared the will invalid, and carried out the inventory.
Prasutagus' wife was Boudicca. She was described as being a large woman, with flaming red hair. Her name in the Brythonic language meant victor. Boudicca had expected that the previous relationaship with the Romans would carry over to her, and her daughters. This was not to be the case. Catus had decided to make an example of the Iceni.
Boudicca and her subjects were incensed by the incredible lack of tact in which the matter was being carried out by Catus. Boudicca then declared herself the leader of the Iceni. Catus had Boudicca flogged, and had her two daughters raped. The property of the Iceni was then declared forfeit to the Romans, and seized. The Iceni rallied around Boudicca, taking up arms in a challenge to the imperial authority. They were joined by the Trinovantes, who were tired of the high taxes, misappropriation of their lands, and the expensive temple that was built in the memory of Claudius in the city of Camulodunum, modern Clochester. With the backing of this army, Boudicca sacked the cities of Camulodunum, Londinium, (London) and Verlanium (St Albans).
Boudiica's army at the sack of London was exceptionally savage. According to Roman historian Tacitus, the Roman women were rounded up, taken to a grove that was dedicated to the worship of the Celtic war goddess, Andraste, where they were murdered, had one of their breasts cut off and stuffed into their mouths, and then were impaled with large skewers. This was in some ways a cruel parody of the rape of Boudicca's own daughters. It may have also been in response to the savage slaughter of Druids at Mona earlier in 61 AD. It may also have been a play at winning the battle in an all or nothing tactic.
Boudicca's rebellion was destined to fail. The Roman commander in chief, Suetonius, rallied a force of Roman legionnaires and friendly Britons that number 10,000. The Roman army took up positions at the edge of a forest, near a narrow gorge. The Britons then came with their forces, including a number of chariots, used to transport both the warriors and their families. (The Celts would often go into battle with women and children, away from the battle, shrieking and screaming, in attempts to unnerve the enemy.)
Suetonius' forces were able to decide the way the battle was fought. Because the Britons army was hemmed in by the woods, and the small opening , and the fact that the Romans were on foot, the chariots became a hindrance, as there was no way to manuver them. The battle became a rout in favor of the Romans. It was reported that the Romans didn't collect many prisoners that day. Women and children were put to death. Boudicca poinsoned herself, rather than end up an amusement for the Romans.
Boudicca's revolt initally caused an increase in the severity of the Roman rule. The Romans became more determined to subdue the Celtic tribes that were not completely under their domain. However, it also made the independent Celtic tribes, and those with only a nominal allegiance to Rome, more determined to hold out.
Suetonius' successor, Pretonious Turpilanius, decided to let the Britons guide themselves. This action wasn't very popular with a number of the Romans. Tacitus caled it "Cowardly Inactivity". However, at this same time, Britain was quiet, and no overt revolts occurred.
Boudicca's revolt didn't free the British tribes of the Romans. It also didn't result in any of the lands of the Iceni or the Trinovantes being returned. What it did show was that the Celts could not unite to fight a common enemy. The Roman legions in Britain were filled with numbers of Gaulish soldiers, cousins to the British. And the use of the allied British tribes against the Iceni also showed the lack of unity the Celts were famous for.