Ninety-seven years elapsed from the time when Roman troops had entered, subdued, and again abandoned the great island in the north-western ocean, before the Roman government resolved to repeat the voyage and permanently to occupy Britain. Certainly Caesar's Britannic expedition had not been, like his campaigns against the Germans, a mere forward movement of defence. So far as his arm reached, he had made the individual tribes subject to the empire, and had regulated their annual tribute to it in this case as in Gaul. The leading tribe, too, which was to be firmly attached to Rome by its privileged position and thereby to become the fulcrum of Roman rule, was found; the Trinovantes (Essex) were to take up on the Celtic island the same part--more advantageous than honourable--as the Haedui and the Remi on the Gallic continent. The bloody feud between the prince Cassivellaunus and the princely house of Camalodunum (Colchester) had been the immediate cause of the Roman invasion; to reinstate this house Caesar had landed, and the object was for the moment attained. Beyond doubt Caesar never deceived himself as to the fact that the tribute, as well as the protectorate, were in the first instance mere words; but these words were a programme which could not but bring about, and was intended to bring about, the permanent occupation of the island by Roman troops. Caesar himself did not get so far as permanently to organise the affairs of the subject island; and for his successors Britain was a perplexity. The Britons who had become subject to the empire certainly did not long pay--perhaps never paid at all--the tribute which was due. The protectorate over the dynasty of Camalodunum must have been still less respected, and had simply as its effect, that princes and scions of that house again and again appeared in Rome and invoked the intervention of the Roman government against neighbours and rivals. Thus king Dubnovellaunus, probably the successor of the prince of the Trinovantes confirmed by Caesar, came as a refugee to Rome to the emperor Augustus, and so, later, one of the princes of the same house came to the emperor Gaius.[97]