The Mercenary Salmon Fly was designed by Peter Sheldon a prolific catcher of Salmon the length and breadth of Scotland.  It is as effective for Sea Trout as it is for Salmon and will get a fish when other options have failed.   Justin Maxwell Stuart from WhereWiseMenFish says -In low-water and bright sunny conditions on the Tweed Peter gave me this fly to try having fished Upper Fllors without joy all morning.   The result was 2 Salmon and 2 Sea Trout when nobody else fishing that day touched a fish!""