It was opened in 1796. Its construction was delayed by soil movement and it was probably the resulting movement that lead to the tunnel having a slight 'S' bend in its length. There is room for two 7 ft beam boats to pass. The tunnel passes underground alongside another Grand Union Canal feature, Drayton Reservoir from which the feeder enters the canal at the east end of the tunnel.
This cache is a short walk from 2 of our other caches, Shafted and BRICK 2 - Return of BRICK and is a short way away from the actual tunnel. If doing this one individually, the parking waypoint is the best access and it can then be done as a cache and dash.
Please be careful if children are with you as although GZ is away from the canal the banks may get slippy in wet weather.
You are looking for a small lock and lock containing a log, pencil and some swaps.