Cassivellaunus. 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 well have been a key figure in the political development of south-eastern Britain before the Roman conquest. Caesar recounts that before his invasions, Cassivellaunus had been in a continual state of warfare with neighbouring tribes. His territory is described as beginning some 75 miles from the sea, and on the far side (that is, on the north bank) of the Thames. This places him in the Chilterns and suggests that he may have been the first local chieftain to found a kingdom here which was later to dominate most of south-east England under the tribal name of the Catuvellauni. His abilities as a war leader are confirmed by his selection by the British, even those he had recently been fighting, to lead the opposition to Caesar. His subsequent handling of his forces and his use of guerrilla tactics, which prevented Caesar from achieving the total victory he was seeking, suggest a shrewd military mind. The location of his stronghold is uncertain but Wheathamstead near Welwyn is possible.

Keith Branigan

Cassivellaunus (kă´sĬvĬlô´nəs), fl. 54 BC, British chieftain, a leader in the resistance against the invasion of Julius Caesar in 54 BC Caesar crossed the Thames River into Cassivellaunus's home country. Aided by discontented British tribes, he attacked Cassivellaunus in his strong fort in the marshes (probably at Wheathampstead, Hertfordshire) and drove the Britons out with heavy losses. Cassivellaunus sued for peace, which Caesar granted in return for hostages and an annual tribute.