Out riding along the canal and spotted a black ferret that I have now been informed is a Mink!
Does this need reporting and if yes who to?
(Investigator Arkady Renko, perhaps?)

The local Mink Hound pack?

Yes you should report it. Mink aren't native, and they like to eat native species such as water voles which are protected. Try you local Enviroment Agency officer. They will probably put down a humane trap to try and catch it if it's in a built up area.

if you're in lancashire there are shedloads , they live i the ribble and prey on everything. one attacked my canoe once .