About Clapham Junction Station
Clapham Junction railway station is a major railway station and transport hub near St John's Hill in the south-west of Battersea in the London Borough of Wandsworth. Despite its name, it is not located in Clapham, a district situated some 1.5 kilometres (0.93 mi) east-south-east of the station.
Routes from London's south and south-west termini, London Victoria and London Waterloo funnel through the station, making it the busiest in Europe by number of trains using it, between 100 and 180 per hour except for the five hours after midnight. The station is also the busiest UK station for interchanges between services.
You're looking for a cache in a busy area, so please be stealthy.