In AD 60, one leader who chose to fight was Queen Boudicca of the Iceni tribe.
When the Romans invaded, the Celtic tribes had to decide whether or not to fight back.
Following the death of her husband, King Prasutagus, Boudicca raised an army of Celts to fight the Romans. They marched towards the city of Colchester which the Romans called Camulodunum.This was the Roman capital of Britain.
Thousands descended on Colchester. They fought fiercely, burning buildings and killing hundreds of men, women and children.
Having captured the city they moved on to London, which the Romans called Londinium and then St Albans (another important Roman town).
When the Roman army heard about this, they turned back from their campaign in Wales to face Boudicca.