It started with an argument that developed as the night wore on: famous American trout fisherman and fly-tier Andre Puyans was adamant that the Matuka pattern of flies was invented in the United States.
"No, it comes from the Maori name for the bittern, a bird with brown feathers," we insisted. "BS!" he said - well, something like that in as many words.
It was the annual conclave of the Federation of Fly Fishing in West Yellowstone, and it was a regular trip when we were involved in the trout fishing and travel business. All the famous names in American fly-fishing literature and tackle were there, vying with each other for the limelight.
On one occasion Lefty Kreh, a household name in saltwater fly-fishing, was giving a casting demonstration and explaining how tailing loops caused wind knots in the leader. The solution was to apply power smoothly on the forward stroke which prevented the rod tip from snapping down and the line hitting itself, causing the knots which bedevil many casters. He spotted the Kiwi watching and asked: "What do yoo Noo Zeelanders do about tailing loops?"
We couldn't help ourselves and replied innocently: "We don't really worry about them. We're too busy catching fish."
Which is true. Americans study the theory and literature to such an extent that many executives will spend their lunch hours practising their casting at the San Francisco Fly Casting Club's pool downtown, without ever putting a fly in front of an actual fish. It's like an Olympic swimming pool, set up solely for casting.
It says volumes about the value of our trout fishing compared with that found in other countries.
But the Matuka discussion carried on well into the night, fuelled by good American whisky, and ended in a stand-off. So we tracked down the editor of the prestigious Fly Fisherman magazine, John Randolph, and suggested he might be interested in an article about the origins of the Matuka style of trout flies. "Good idea," said John enthusiastically.
Back in Rotorua we talked to Frank Lord, one of the legends of trout fishing in Rotorua, and Pat Burstall, the former conservator of wildlife for the Department of Internal Affairs, which ran the trout fishery in those days. And so the story emerged.
When trout were first introduced to the Lakes region in 1883, they found a rich environment inhabited by small native fish, mainly bullies and the koaro, a mottled brown fish. Original tackle and flies were patterned on English salmon fishing and the trout grew to salmon-like proportions. But trout fishermen soon discovered that the feathers of certain native birds were a useful resemblance to the koaro, namely the kiwi and bittern.
It was so effective that bittern numbers declined to such an extent that their killing was prohibited and, like the kiwi, they were protected to preserve the remaining populations.
As the koaro were eaten out of existence in the Rotorua and Taupo lakes, so the need for the bittern feathers waned. Smelt were transported from Taupo to the Rotorua lakes as a replacement and, fortunately, they thrived so much that today smelt support healthy populations of big trout in the lakes. The old fly patterns have faded into history, and it is now actually illegal to possess the feathers of the bittern, so the surviving examples of the original patterns are hidden in old tobacco tins of yesteryear.
But the Matuka found its way to the US, where it became popular as a style of tying flies patterned on the original New Zealand fly.
It involves tying a feather along the top of the body so it streams back, and is called a streamer fly.
They use mainly bantam feathers, and in this country they have morphed into the popular range of smelt imitations used today.
Matukas are popular in western US states such as Montana, Wyoming and Idaho, where the best trout fishing is found, and so the story found its way into Fly Fisherman. Randolph was true to his word and Burstall supplied the magazine with some of the original patterns which had been officially preserved.
Ironically, our rainbow trout came from northern California, and our fisheries authorities have since sent eggs back to their homeland to rejuvenate wild stocks which had become weakened through generations of hatchery breeding.
And the following year at West Yellowstone, when we ran into Puyans in the hotel corridor, he didn't say anything; simply thrust out his hand and proclaimed: "You were right!"
It is tempting to add the word "mate", but that would not be true. And trout fishermen never bend the truth, do they?