 These are unique in any of the circular redoubts and are thought to have been added in the mid-19th century.Access to the main gate of the redoubt is across a wooden drop bridge, which is a modern reconstruction of the original, built in 2003 with help from the Royal Engineers.A second entrance from the ditch was created in 1957 by inserting a large doorway through the scarp wall into one of the casemates.