Cassivellaunus sent word to his allies in Kent, Cingetorix, Carvilius, Taximagulus and Segovax, described as the "four kings of Cantium", to stage a diversionary attack on the Roman beach-head to draw Caesar off, but this attack failed, and Cassivellaunus sent ambassadors to negotiate a surrender. Caesar was eager to return to Gaul for the winter due to growing unrest there, and an agreement was mediated by Commius. Cassivellaunus gave hostages, agreed an annual tribute, and undertook not to make war against Mandubracius or the Trinovantes. Caesar wrote to Cicero on 26 September, confirming the result of the campaign, with hostages but no booty taken, and that his army was about to return to Gaul. He then left, leaving not a single Roman soldier in Britain to enforce his settlement. Whether the tribute was ever paid is unknown.