Market Estate, Islington. Caledonian Park. Night time sound of foxes mating. I thought they had moved on because of the redevelopment but they are still around! Hurrah! No one knows the precise size of Britain's urban fox population. Local authorities have given up trying to control them and in London - where some experts estimate their numbers at 10,000 - councils distribute leaflets informing householders that foxes are considered wildlife and they should learn to live in "harmony" with them.