In 2010, our agency was briefed by a big brewery to have one last go at reviving a beer that had been in decline for a decade. The previous agency had done seven big brand campaigns for DB Export Gold over that decade, and none had worked. Nobody liked Export Gold much. It wasn't great beer. It had no brewing credentials and a vaguely metrosexual personality that didn't impress men much. Even the client recognised the hopelessness of a beer without a proper story – apparently Export Gold had been invented in the 1990s by the marketing department.

Then I talked to a guy called Doug Banks. Doug's been the head brewer at DB Breweries for over 40 years. I asked him how he felt about this 1990s marketing beer. "Eh?" said Doug. "That couldn't be further from the truth." Then he sat me down in his office in a corner of the building where the marketers never went, and told me a story that nobody else in the company, even the CEO, had ever heard.

"DB Export was created by a man called Morton Coutts. Morton came from a long line of beer brewers. His great-grandfather was a master brewer from Germany. His grandfather was one of the first men to brew beer in New Zealand. And his father built the main trunk line brewery in Taihape at the start of the 20th century. But after becoming incapacitated in the 1919 influenza epidemic, he had no choice but to hand the brewery down to his son Morton, who was 15 at the time.

"Morton turned out to be a beer-brewing prodigy. He built that brewery up, sold it, moved to Auckland, and at the age of 25, built the Waitemata brewery where DB still stands today. Then a few years later, in 1958, the government introduced what was called the 'Black Budget'. Arnold Nordmeyer, the finance minister, decided he was going to raise the tax on a number of things, including imported beer. At the time, New Zealand brewers were making good beer. But if you wanted to drink really great beer, you drank the imported stuff. The Black Budget meant that ordinary New Zealand men could no longer afford to drink the best beer.

"So Morton had an idea. If he could be the first New Zealander to brew the best beer in the world, Nordmeyer wouldn't be able to tax it, and we'd all be able to drink it for a fair price. So he got to work. Harder than he ever had before. He brewed the best beer he'd ever brewed. He called it 'Export' because he dreamt of it holding its own anywhere in the world. And then in 1960, Export won 'Best Beer in the World in Any Class' at the International Brewing Awards – the first New Zealand beer ever to do so. Morton had done it. He'd created a way for ordinary New Zealanders to drink the best beer in the world for a fair price."

I was blown away. The emasculated beer with no brewing credentials and no story, in fact, had the best story I'd ever heard. It was New Zealand's first great beer. It was created by one man working for the good of all New Zealand men. And nobody except Doug, and now me, had any idea this story existed.

"But you know," said Doug, "times changed, and over the years we messed with the recipe and so today, Export Gold is really nothing like that original 1960 brew." Blowing the dust off an old archive, he found Export's original recipe. "Oh yeah, this is very different – 5.35% to begin with, and much tastier. A bit like a modern craft beer."

I asked him if he could make some, and he agreed to. Six weeks later, we tasted the original brew.

The experience of drinking New Zealand's first world-beating beer, just as it was in 1960, was profound. And so we decided not only to tell New Zealanders the untold story of DB Export, but to let them experience it. We made the 1960 brew, put it in the exact bottle it had been in back then, with the same label, and put it in a beautiful box with the whole story printed on the outside.

When we released the Export Original product, sales of Export Gold shot up as people discovered a new respect for the beer's heritage. After ten years of decline, Export Gold got back to the market share level it had enjoyed in the late 1990s at the peak of its success. It took six months.

If creative people are to be great storytellers, we planners need to be great storyfinders. To believe that there's an amazing story about anything. And to go out and ask around until we find it.

For ten years nobody asked Doug. And that was all it took.