Mandubracius of the Trinovant (Essex area)
reported to Caesar that his father, the tribal chief
, had been killed by the Catuvellauni (Herts area
and north of the Thames) who were oppressing
his tribe. It was as good an excuse as any for
Caesar to come again, being promised a safe
landing. He sailed with five legions and over 800
transports, and captured the capital stronghold of
Cassivellanus (probably at Wheathampstead).
Commius negotiated the terms of surrender.


When Caesar arrived in 55BC, he found that
Commius had been taken prisoner. He was
returned with apologies. There was a
temporary peace but Caesar, having thought
that he would receive submission by the
British tribes, was troubled with damaged
transports and attacks, and got away back to
Gaul with dificulty. Commius, with a cavalry
detachment, helped the getaway. Some
histories differ on the early Commius, treating
him as king of his tribe in Britain, who had fled
to Gaul in the first place.