On a warm evening in May we were lucky enough to be invited to the launch of Serpent, a stunning ‘alliance' between Brooklyn Brewery and Thornbridge. Daniel Neilson recounts the story

On a warm evening in May, behind a small, inauspicious door, was a fairytale world of beer. A magical labyrinth of rooms filled with weird, the wonderful and the downright bizarre. In one room, Brooklyn Brewery's head chef Andrew Gerson served a salmon dish… directly on to my hand. I licked it off and took a swig of Sorachi Ace. Brooklyn Brewery's Brewmaster Garrett Oliver did the same. In another room, The Graveltones were knocking their frenetic rock to a bouncing room of fans. There was a photo booth, secret talks in secret rooms, games, a pizza parlour, a man was carrying a six-foot star for no apparent reason. All the beer was free, from the ultra-rare Brooklyn Brewery Ghost Bottles, plus dozens of one-off beers from Beavertown and half a dozen other London breweries. This was the Brooklyn Beer Mansion, as part of the Brooklyn Mash tour. And you know what… that wasn't even the best of it.

Upstairs in the ‘Brewer's Room' was a very special launch. Jim Harrison, owner of Thornbridge had come down from the Peak District, Garrett Oliver had come over from New York. The Brooklyn Beer Mansion, you see, would also see the launch of Serpent, a remarkable collaboration between Thornbridge and Brooklyn. It is a beer gobsmacking in its ambition. It is a Belgian golden ale – simple enough (but still tough to do well). But Garrett wanted to barrel age it. Fine.. an added layer. But the barrels had to come from upstate New York and shipped to the Peak District. OK. Dozens arrived. Oh, and then instead of regular fermentation, the golden ale was to sit on cider lees, the natural wild yeasts that ferment apples into traditional ciders, harvested from the country's best cider maker Tom Oliver – these needed to be sent up regularly from Herefordshire. It then needed a year in barrel, before the most skilled process of all – blending them.

I'd tasted the beer out of the barrel on a visit to Thornbridge around a year ago, and now, on a rooftop terrace on a quiet London backstreet, Garrett Oliver is pouring a glass of a beautifully golden ale out of a champagne bottle. But it's not just a golden ale. Sure, there's a taste of cider, and maybe reminiscent of an oaked white wine. It's spritzy like a British sparkling wine, yet grounded with an earthy funkiness. It's a beer unlike anything I've ever had. It's a masterstroke of ingenuity and perseverance, and let's not forget the unbelievable skill of Thornbridge brewery Rob Lovatt and Garrett Oliver to see through the process and turn out a beer that has never been done before. It silences the terrace. I pour more and drink some more and chat some more, and then wander back down the rabbit hole.