One of our members found this as we were rubble clearing. It's a Victorian 'Friction Tube' used for firing artillery pieces and was basically a trigger.
For the technical minded, it is a Land Service (Short) Mk.II. The tube was inserted into a vent in the breech of the artillery piece, it was primed with powder and threaded with a lanyard. When pulled, this caused a spark, igniting the powder and firing the gun.
Although the guns of the Redoubt were never used in action, the gunners used to regularly practice on floating targets in the harbour.