Slide a 2mm black or black nickel tungsten bead onto a size 16-20 hook, seat it at the eye, and start the white translucent Sumo 30 den behind it.
Wind the thread back to the bend in a thin layer, then tie in the peacock UV tinsel and wrap it forward to just behind the bead as the underbody.
The tinsel underbody is the whole trick: rather than mixing synthetic sparkle into dubbing. You put the shine underneath and let it show through, which reads as depth rather than glitter.
Tie in the mayfly yellow micro wormy body at the rear and wind it forward over the tinsel in touching turns to about the 75% mark. The material is translucent, so the peacock UV flashes through the wraps and gives the body its juicy look.
Dub a short thorax of natural eastern grey squirrel behind the bead, then set a few partridge barbs each side as legs swept back to the hook point.
Whip finish behind the bead and pick the thorax out lightly. Tied small - 18 is the tyer's size. This is a late autumn and winter fly and it accounts for a lot of grayling.