I can remember when Taverham Mills was sold, a 25acre lake, stretch of river, a house and I think another 20acres of land. The Carp Society put in a bid, but were outbid by Anglian Water with a bid for £1,000,000. Anglian Water managed to fence the lake trapping otters inside the fence.
What irritated me is I had built the fence around the roadside and the woods at the back when I ran it and had no problems. Anglian Water ripped the fence down to rebuild it leaving it down for weeks, allowing otters to get in. Those same otters were getting the barbel and carp in the river before they got into the lake, so AW would have known otters were in the area.