Fish it whenever a dry alone is optimistic and a nymph alone is dull: cold mornings before the hoppers move, quick pocket water where fish hold deep, the spring melt on a river like the Eucumbene when the water is up and the fish are down. It is the rig for a creek too thin and too quick for an indicator, and for a gorge where every pocket is a metre deep and a metre long.

It is also the honest answer to not knowing what the fish want. The dry asks one question and the nymph asks the other, and the fish answer whichever they like.

A four or five weight, a floating line, a nine-foot leader to 4X or 5X. Tie on a dry that floats hard: a Stimulator or Royal Humpy in rough water, a Royal Wulff or a foam hopper on a creek, a small Klinkhammer in slow shaded pools where a big dry would frighten the fish.

From the bend of the dry’s hook, tie 40 to 60 cm of tippet and a tungsten nymph: a Pheasant Tail or Hare’s Ear in 14 to 16. The dropper length is the depth you want the nymph to fish. In a pocket a metre deep, go a metre; on a creek bend a foot deep, a foot is plenty and more is a snag.

Match the bead to the water, not to the dry. If the dry keeps sinking, the nymph is too heavy for it; go to a bigger dry before you go to a lighter nymph.

Cast upstream and short. Land the dry at the head of the pocket or on the seam, and let the pair drift back to you with the fly line off the water. Watch the dry. When it dips, twitches, stops or does anything a dry drifting alone would not do, set. When a fish eats the dry itself, which happens often enough to keep you honest, set a little slower or you will pull it away.

One or two drifts through a pocket, then move. The rig covers water fast, and the first drift is the one the fish sees clean.

Tangles, mostly. Open the loop, slow the cast, and stop trying to throw it as far as a single dry. If the nymph keeps wrapping the dry, the dropper is too long for the cast you are making.

The second failure is fishing the dry and forgetting the nymph is there. Half the takes are subtle: the dry slides sideways, or pauses. Set on all of them. A missed set costs nothing; a missed fish was the whole cast.

The rig lives in broken water, and broken water hides the rock that ends a day. Boots with grip, a staff in anything pushy, and fish the pocket from the bank when the lie itself is the only place to stand. Two flies also means two hooks; land a fish with a net, not a hand, and mind the trailing nymph when you release it.