High Quality Content by WIKIPEDIA articles! Waltham Common Lock (No 10) is a lock on the River Lee Navigation at Waltham Cross. The lock is located in the River Lee Country Park which is part of the Lee Valley Park and stands close to the Showground site now known as the Broxbourne White Water Canoe Centre - venue of the 2012 Olympics canoeing event. At the tail of the lock is the Powdermill Cut dug in 1806 to connect the Waltham Abbey Royal Gunpowder Mills directly to the then new Navigation.