When the Emperor Valerian was captured by the enemy what the empire needed was a trusted, capable, firm set of hands to take on the imperial mantle. In retrospect, that probably wasn’t his son Gallienus. For the next eight years Gallienus would rule as sole emperor and proceed to lose two thirds of the empire, leaving Rome at its weakest position in centuries. Part I of ‘Gallienus’ Guest: Associate Professor Caillan Davenport (Head of the Centre for Classical Studies at the Australian National University).