There has been a lock on the River Thames at Teddington since 1810. The current lock is a complex of three locks and a weir. The lock is on the southern Surrey side of the river.
The river downstream of the lock, known as the Tideway, is tidal, though the Richmond Lock barrage downstream limits the fall of water to mainntain navigability at low tide. The boundary point between the Port of London Authority, which is the navigation authority downstream, and the Environment Agency, which is the navigation authority upstream is marked by an obelisk on the Surrey bank a few hundred yards below the lock.
The lock complex consists of three locks, a conventional launch lock, a very large barge lock and a small skiff lock. The barge lock has an additional set of gates in the middle so it can operate in two sizes.
The large bow shaped weir stretches across to Teddington from an island upstream of the lock which also acts as the centre point for the two bridges making up Teddington Lock Footbridge.
The cache is hidden in a tree about 10 metres away from the path leading from the footbridge towards Kingston.