It is 150 years since HMVS Cerberus arrived in Port Phillip Bay, on 9 April 1871. The British - built Cerberus was commissioned as a coastal defence ship to safeguard Melbourne, the Australian colonies' largest and wealthiest city in the late 19th century. The small and unconventional looking vessel was once our most powerful warship and notable for her place in the evolution of warship design; this breastwork monitor was iron clad and steam powered, with raised revolving gun turrets on a central superstructure and with a low freeboard.