West Warwick Reservoir, located in Walthamstow, London, is part of the Lee Valley Reservoir Chain, providing drinking water to London. Completed in 1895, it was named after the Countess of Warwick. The reservoir is within the Walthamstow Reservoirs, a designated Site of Special Scientific Interest (SSSI), and is popular with birdwatchers, anglers, and naturalists. However, access is restricted to permit holders. It plays an important ecological and recreational role in the area, contributing to both wildlife conservation and local leisure activities.