Wild Things columnist Eric Brown learns of anti-mink measures introduced at a Bexley nature reserve and recounts his own worrying encounter with the dangerous species.

Nothing could be seen of it except for a pair of large, dark, staring eyes and the top of a black head above water disturbed by its v-shaped bow wave. It moved quickly past my wife and I as we swam in the lake, scrambled from the water and revealed itself as a mink. Then it headed towards a tree where our toddler son was playing with toys. Cue pandemonium. My wife reached our son first and scooped him up away from danger as the startled mink disappeared down a hole in tree roots. Mink, with their razor-sharp teeth and claws, are among the most fearless and devastating small predators around. Larger than a grey squirrel but smaller than an otter, they have voracious appetites and will eat almost anything. One has been photographed killing a grey heron. My sighting occurred in southern Finland around 1980. Within a few years of mink being discovered there the enormous lake had been almost cleared of fish, a local delicacy that sustained generations of people. Next morning I found smoke spiralling up from the tree roots where it vanished and my father-in-law watching over a controlled fire. He later filled in the hole.