The Suffolk Flora Preservation Trust had an open day on the Gromus Valley at Kelsale in Suffolk. One of the most impressive features is a 200 m long medieval dam across the valley. The Trust has used LIDAR imagery to show the extent of the lake.
The dam and lake appear to form part of the hunting estate by the Bigod family at Kelsale. The earliest reference to the lake appears in the Patent Role of 1281 (details).