Charles and Singleton have explained why Cassius Dio's claim (60.21.2) that elephants were among the equipment prepared for use in Britain during the Claudian invasion of a.d. 43 is probably untrue, if one assumes that by ‘elephant’ he means the animal of that name. It is argued here that the best explanation of this apparent error is that Dio preserves a reference to a type of military machine, probably a siege-tower, rather than to the animal of this name.