Ice, we are warned, can harbour terrifying amounts of bacteria. Top bartenders would no more handle an ice cube than they would stick a finger into your mojito, but their dogged pursuit of a pure, slow-melting, crystal-clear cube has taken a slightly surreal twist, with the use of various filtration and freezing processes that may or may not have any basis in science. “We double-freeze our cubes,” informs Chloe at exclusive London bar Milk and Honey. “We freeze them, thaw them, and freeze them again. But that’s for our members only. Everyone else gets normal frozen ice.” There’s a more egalitarian approach up the road at Japanese bar Shochu Lounge, where water subjected to a long freeze (“4 hours, to increase clarity and compactness”) before huge blocks are mounted on full display; bartenders then chip away with tools more suited to a glacial expedition. “We have a large ice saw with serrated teeth,” explains barman Tony Congliari, “and ice picks in 3 different styles to chip off smaller pieces.”

Demand for gourmet ice in Europe is small compared to the US, but is growing steadily. “Refrigeration solutions” company Hubbard produce machines that churn out crystal clear “supercubes” at a rate of up to 33,000 per day. Other businesses make ice to order in various shapes and sizes while extolling the purity of their water sources. Highland Ice use soft water from Loch Lee in the Angus Glens, while farmer Phil Mann draws spring water from deep beneath his Ludlow farm to make “Shropshire Rocks”. He’s confident that the public will become unhappy with the opaque cubes that emerge from domestic freezers with rogue peas balanced on top, and carrying a whiff of frozen prawns. “There will be people worried about what they add to their drinks, and spring water ice will take off in the same way that spring water has.”

Alex Turner at IP Bartenders isn’t quite convinced. “I’m passionate about ice itself, rather than double frozen water from some protected Arctic source. We just use filtered tap water – the trick is to use lots and lots of ice. It keeps your drink cold, the ice doesn’t melt so quickly, so your drink stays strong.” Glenn Harding at Global Ice chortles merrily at the double-freeze concept; he sells tons of ice cubes every day made with normal tap water. Well, normal-ish. “We purify using a reverse osmosis filtration system, and a UV filter.” So, for that unique taste of unfiltered frozen water, you’re probably better off making some yourself. For free.