The Lady Amherst is a classic fly, though it is not Victorian in age, nor British in origin. It was actually conceived by G. Bonbright, and is thought to be of Canadian origin.
Anyways. Most often it is seen tied on the larger end of the salmon fly scale, 5/0-6/0 range, and in the past I've tied it thus (picture below)
However, it is also recommended by the originator that it can be tied in smaller sizes, but using Amherst tail slips for the wing rather than tippets.
So, I tied up the smaller to go with the big one I already have.
Hook is 1/0, there are no horns on the small one (tyers oversight)
I should really get a picture of both together.
Lady Amherst 1/0
Lady Amherst 6/0