Whether hunting monsters in Loch Ness or big cats on the moors, people have long searched for mysterious wild beasts, and they may finally have something they can sink their teeth into.

The “clearest ever” photo of a big cat prowling the British countryside has been unearthed and included in a new documentary.

In an image found among decades-old mail, a muscular cat with the appearance of a panther is seen lying among grass and scrub.

The undated photograph has been included in a new Amazon Prime documentary titled Panthera Britannia Declassified, in which those in the search for legendary animals state that the cat’s size and muscularity suggest it could be exciting proof of big cats in the UK.

It is claimed in the documentary that the image represents the “best photo of a British big cat that exists”.

The photo unearthed in a filing cabinet was found with some text on the reverse side, explaining that the image was “the last sighting” of the “Beast of Smallthorne”, an area of Stoke-on-Trent