The Brigante queen Cartimandua is often regarded as a traitor by those who read about Roman Britain. It is perhaps unfair because as a young girl she was married to an older man that the history books record as Venutius.
During this period, the Roman Empire invaded Britain because to the south of the Isle, a warrior king known as Caractacus seized an immigrant kingdom of Attribate. These people came from today's Belgic regions of Europe. Julius Ceaser left them lands in Britain after his raid on Britain during the Gaul Campaign.
After almost 100 years the Attribate enjoyed trade into Britain via their kingdom. Caractacus took their land, thinking Rome would have to go through him as the new ruler.
He was mistaken and instead gave Rome an excuse to invade the Isle of Britain. Caractacus kingdom quickly fell before the Roman army but he managed to flee to Kingdoms in today's Wales. The Roman Empire pursued Caractacus but he fled these kingdoms after they fell to Rome too.
When Caractacus stood before Cartimandua, she may have decided he was more trouble than he was worth and could see she and her Brigante had no way of confronting this Roman superpower empire from mainland Europe. Instead she chained Caractacus and handed him to Rome, thus securing client kingdom status for the Brigante and keeping Rome at bay. Perhaps Caractacus was passing through the Brigante trying to escape to Caledonia. (today's Scotland.) Whatever reason for Caractacus entering the Brigante lands, he would bring angry Romans hot on his heels.
This caused a rift between Cartimandua and her older husband Venutius who did not favour friendship with Rome. He was chased out off of the Brigante lands. This left Cartimandua free to rule the Brigante as a client queen supported by Rome. She had Pict enemies to the north and was able to play Rome off against them. She ruled for 26+ years and refused to aid Boudicca and her Iceni rebellion in 61 AD.
Her rule ended in 69 AD when the year of the four emperors caused mayhem among the Roman Empire's legions. Her divorced husband Venutius retook the kingdom, angry that Cartimandua had taken with his young armour bearer named Vellocatus.
(Some people believe the King Arthur, Lancelot, and Queen Guinevere story come form this time by word of mouth. Then hundreds of years later Christian priests corrupted the story to meet Christian ideals of Britons fighting Angle and Saxon pagans hundreds of years later.)
Cartimandua was rescued and brought south by Roman soldiers, but her Brigante kingdom could not be saved from occupation by Venutius. She went into exile somewhere within the Roman Empire and faded from history. No one knows what became of her or when she died.
Her divorced husband Venutius would lose the Brigante to the Roman Empire when Vespasian became the fourth emperor of that year, finally bringing stability to the Roman Empire but a brutal war in the Brigante that was sporadic and continuous for decades.