The sketch above is part of John Nash and David Gibbins rather beautiful map of Lea Marsh produced in 1981. It shows the Lea with the tow path and then Sandy Path. The vertical line (the row of dots) to the right of the map is the borough bounday between Walthamstow and Leyton where the Black Poplars are. Although the area used to be just open marsh, LVRPA has enclosed it with a wooden fences and keeps ornamental cattle there much of the year.
The extract below is from a web site cataloguing WWII V2 Rocket Attacks. It reveals that bomb crater pond was originally a 55ft diameter crater resulting from a V2 rocket that arrived on 11/Feb/1945 at 14:52. According to the web site, one person was injured (the James Latham timber yard on the other side of the Lea was also covered in mud). The rocket was launched from the Hague by Artillery Regiment 3./902.
The Second World War probably changed Lea Marsh more than any other event, since huge amounts of building debris was dumped on Porters Field (including at least one unexploded bomb) immediately after the war.