And Wandsworth council in south-west London is pondering its defence strategy after confirming that the deaths of a young swan and other wildlife on Wandsworth Common in the summer may have been caused by a mink.
It is the closest sighting to central London of the animal, described by naturalists as a 'ruthless predator'.
Since fishermen first spotted it on an island on the common's lake, council officers have made repeated attempts to capture the animal using humane traps - but so far it has evaded them.
The officers fear that unless captured, the mink will cause havoc next spring, especially when wildfowl start mating.
One councillor said she was 'deeply concerned' at the possible devastation of Wandsworth's wildlife, although a council spokesman yesterday said that the creature had not been 'officially identified as a mink' and would only confirm that it was a 'mink-like animal'.
Mustela vison - American mink - are descended from those introduced to Britain in 1929 for the purpose of fur farming. Sightings of escaped mink were first reported in the 1960s, bringing fears that the animals would upset natural ecosystems.
The luxuriously-pelted creatures have been blamed for the demise of the otter, as well as the disappearance of ground-nesting birds such as coot, moorhen and little grebe. They have also been blamed for damage to fish and poultry farms and have ended free-range poultry farming in some areas.