The mink we have in Britain are none native and are originally from American. The American mink Neovison vison were originally import to the UK to be used for fur-farming.
In continental Europe, there is also a European mink Mustela lutreola, a completely different species and now very much endangered. The European mink has never been recorded in the UK.
The UK’s wild population of American mink originated mostly from mass releases of mink from fur farms in the 1990s. Many people will remember these dramatic events for the 100,00’s of mink involved. However, a wild population was established decades earlier from multiple escapes (and perhaps deliberate releases) all over the whole of the UK.
On the River Witham there is a significant population of American mink Neovison vison which are having a negitive effect on the local water vole population.