Camulodunum (Colchester). The Atrebates tribe whose capital was at Calleva Atrebatum (Silchester) had friendly trade and diplomatic links with Rome and Verica was recognised by Rome as their king, but Caratacus' Catuvellauni conquered the entire kingdom some time after AD 40 and Verica was expelled from Britain. Caligula may have planned a campaign against the Britons in AD 40, but its execution was unclear: according to Suetonius' The Twelve Caesars, he drew up his troops in battle formation facing the English Channel and, once his forces had become quite confused, ordered them to gather seashells, referring to them as "plunder from the ocean due to the Capitol and the Palace". Alternatively, he may have actually told them to gather "huts", since the word musculi was also soldier's slang for engineers' huts and Caligula himself was very familiar with the Empire's soldiers. In any case this readied the troops and facilities that would make Claudius' invasion possible three years later. For example, Caligula built a lighthouse at Bononia (modern Boulogne-sur-Mer), the Tour d'Ordre, that provided a model for the one built soon after at Dubris (Dover). Claudian preparations In 43, possibly by reassembling Caligula's troops from 40, Claudius mounted an invasion force under overall charge of Aulus Plautius, a distinguished senator. A pretext of the invasion was to reinstate Verica, the exiled king of the Atrebates. It is unclear how many legions were sent as only the , commanded by future emperor Vespasian, was directly attested to have taken part. The , the (later styled ) and the (later styled ) are known to have served during the Boudican revolt of 60–61, and were probably there since the initial invasion, but the Roman army was flexible, with cohorts and auxiliary units being moved around whenever necessary. Three other men of appropriate rank to command legions are known from the sources to have been involved in the invasion. Cassius Dio mentions Gnaeus Hosidius Geta, who probably led the IX Hispana, and Vespasian's brother Titus Flavius Sabinus the Younger. He wrote that Sabinus was Vespasian's lieutenant, but as Sabinus was the older brother and preceded Vespasian into public life, he could hardly have been a military tribune. Eutropius mentions Gnaeus Sentius Saturninus, although as a former consul he may have been too senior, and perhaps accompanied Claudius later. Crossing and landing The main invasion force under Aulus Plautius crossed in three divisions. The