The story goes that someone in Kendal was trying to make clear glacier mints, but let the sugar overcook, and saw that the mix had become cloudy rather than clear. He poured it our anyway, and the result was Kendal Mint Cake
Production started in 1869 and it was sold at Kendal railway station among other places. Hence its fame spread to across the north of England. Kendal Mint Cake got two big publicity boosts from being used by Shackleton on has Arctic expeditions and by the first Everest expedition
Later, in 1953, the successful British expedition that climbed Everest used Kendal Mint cake to bolster their energy. And many other expeditions have opted to carry it because of its high glucose content
Apparently New York customs authority would not allow it into the USA in 1970, as what they saw was not strictly speaking cake, and it had to be tipped into the sea. Funny people the Americans!