British chief or king. Cassivellaunus is known only from the war diaries of Julius Caesar and Dio Cassius' later derivative account of Caesar's invasions of 55 and 54 bc. Nevertheless, he may have been a key figure in south‐eastern Britain before the Roman conquest. His territory is described as beginning some 75 miles from the sea, and on the far side of the Thames. This places him in the Chilterns and suggests that he may have founded a kingdom there under the tribal name of the Catuvellauni. His abilities as a leader are confirmed by his selection by the British to lead the opposition to Caesar.