Start brown olive UTC 70 on a size 14 curved nymph hook, tie in small copper wire and run the thread up leaving about a quarter of the shank clear at the front for the thorax, building the taper as you go.
Strip a peacock quill with your fingers, tie it in and wrap the body forward, keeping the wraps smooth.
Rib forward with the copper wire. Stripped peacock quill underneath and copper wire over the top gives you two layers of segmentation, which is why this old pattern still looks so alive up close.
Tie eight to ten pheasant tail fibres in with the tips facing forward, centred on top, then trim the butts and keep the thorax area smooth.
Tie in Uni-Stretch for the gills, figure-eighting it down. White ostrich herl was almost certainly the original material here if you want to be faithful.
Tie a second strand of peacock herl in just behind the gills and wrap it so it flares out fluffy for the thorax.
Pull the pheasant tail over the top, take a couple of wraps to cover the butts, pull the gills straight up and trim them even, then whip finish.