The boy Deri did not exist. But Caratacus and the Roman emperor Claudius did.
Caratacus was betrayed by Queen Cartimandua of the Brigantes tribe. He was taken to Rome in chains. Just when he was expected to die, he made that famous speech in the senate and Claudius spared him.
Nine years later, in AD 60, Queen Boudica led a rebellion against the Romans with her Iceni tribe. Many Romans in Britain were massacred. But in the end the Romans won.
They stayed until about AD 409. The city of Rome was under attack and the Romans in Britain were sent back to fight for their city. They never returned.
By then the Christian religion had come to Britain, and the druid religion died away. There would be no more spilling of guts … you’ll be pleased to hear!