Prince Frederick's Bastion was constructed as part of the first phase of main construction of the Chatham Lines in 1755-1758. It was the bastion at the north-east corner of the Chatham Lines where the east flank turned west back toward the river north of the Royal Dockyard. It was eventually supplanted by a new line of defences, the Lower Lines, that was constructed during the Napoleonic Wars. Like the rest of the chatham Lines the bastion was declared obsolete in 1860 by the Royal Commision.