"Nobody knew what on earth was going to happen"

Nobody knows what on earth did happen! The account here is elaborated from passages in Suetonius's The Twelve Caesars and Cassius Dio's Roman History, both of which refer to an abortive invasion attempt on Britain, which saw Caligula declaring war on Neptune instead of the British tribes.

During the course of these proceedings, Caligula seems to have accepted the "surrender" of the British chieftain, Adminius (one of the sons of Cunobelinus, King of the Catuvellauni). But it is more likely that Adminius was seeking refuge following a dynastic dispute within Britain.