In the late 1930s and early 1940s the German air force carried our aerial reconnaissance of British defences. They identified a number of sites of possible military nature and depicted them on a 1940 map. The map was at 1:50,000 scale, however, and reflects the uncertain nature of the Germans' information. The map included a short trench system here. The 1946 RAF vertical photo shows a single trench parallel to Plumpudding Island, with interrupted ramparts of soil on either side (possibly an anti-tank defence?). May have associations with First World War practice defences to the east being taken for new defences by the Germans.