The Thames was crossed--apparently between Kingston and Brentford above London--by the Romans; they moved forward, but made no real progress; the general achieved no victory, the soldiers made no booty, and the only actual result, the submission of the Trinobante in the modern Essex, was less the effect of a dread of the Romans than of the deep hostility between this canton and Cassivellaunus.

The danger increased with every onward step, and the attack, which the princes of Kent by the orders of Cassivellaunus made on the Roman naval camp, although it was repulsed, was an urgent warning to turn back.
The taking by storm of a great British tree-barricade, in which a multitude of cattle fell into the hands of the Romans, furnished a passable conclusion to the aimless advance and a tolerable pretext for returning.

Cassivellaunus was sagacious enough not to drive the dangerous enemy to extremities, and promised, as Caesar desired him, to abstain from disturbing the Trinobantes, to pay tribute and to furnish hostages; nothing was said of delivering up arms or leaving behind a Roman garrison, and even those promises were, it may be presumed, so far as they concerned the future, neither given nor received in earnest.
After receiving the hostages Caesar returned to the naval camp and thence to Gaul.

If he, as it would certainly seem, had hoped on this occasion to conquer Britain, the scheme was totally thwarted partly by the wise defensive system of Cassivellaunus, partly and chiefly by the unserviceableness of the Italian oared fleet in the waters of the North Sea; for it is certain that the stipulated tribute was never paid.
But the immediate object--of rousing the islanders out of their haughty security and inducing them in their own interest no longer to allow their island to be a rendezvous for continental emigrants-- seems certainly to have been attained; at least no complaints are afterwards heard as to the bestowal of such protection.
The Conspiracy of the Patriots The work of repelling the Germanic invasion and of subduing the continental Celts was completed.

But it is often easier to subdue a free nation than to keep a subdued one in subjection.
The rivalry for the hegemony, by which more even than by the attacks of Rome the Celtic nation had been ruined, was in some measure set aside by the conquest, inasmuch as the conqueror took the hegemony to himself.