EDINBURGH ice man Rhys Ferguson is worried about what Scots drinkers are putting in their cocktails this Christmas.

The businessman who, along with Ilanna Middleton, runs the Edinburgh Ice Company, says he fears bars are cooling their customers drinks with substances that may not be fit for human consumption.

Or worse – they could be using ice made from London tap water.

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Ferguson has been carrying out research into the “traceability” of ice blocks, the large slabs of frozen water that take pride of place in some of the country’s more swanky pubs.

And he has discovered very little of the ice used in Scottish bars comes from Scottish water. Instead, it’s shipped up from south of the Watford gap, and made from hard water.

As bar staff use saws and picks to take chunks of ice from frozen bricks, customers ooh and ah and take pictures for Instagram but almost never ask about the provenance.

According to Ferguson, punters can spend a small fortune on a drink, choose top quality alcohol, maybe an expensive mixer and then dilute it with water they wouldn’t feed to their dog.

“The ice is going into drinks. It makes up a massive percentage of the drinks” Ferguson said. “When you’re putting that ice cube in your whisky, you want the best water you can get.”

He added: “A lot of people don’t want London tap water. Why would you? Here we can just turn on the tap and drink away because it’s brilliant water. It’s better than most of the bottled waters.”

Scotland, Ferguson says, has the best tap water in the world, and therefore the best ice in the world.

“I’m not being all defensive about Scotland as such, but we shouldn’t be having the water being brought up here.”

He did add he was “very happy” to see his ice sold down south.

Ice blocks made from London water are harder to work with, Ferguson says, because of the hard water, packed full of minerals, making it brittle.

He also worries that some of the bars looking looking to save money may be unwittingly using sculpting ice, a cheaper product not fit for human consumption that unscrupulous sellers might use.

In one Glasgow city centre cocktail bar some of the Friday drinkers spoken to by The National late yesterday admitted they had never really thought about the ice going into their drink.

Student Emily, 22, said: “I never think about it in this country. I don’t know why. I’m always really aware of it if I’m abroad.”

Laura, a 35-year-old office worker, said: “I’m too busy thinking about the drink to think about the ice. But I might think about it more now. I’d never drink tap water in London.

The barman doesn’t know where his ice comes from. He said: “A guy in a van drops it off. I’m pretty sure it’s legit. We’ve never had any problems.”

The Bartender’s Guide, also know as How to Mix Drinks or A Bon Vivant’s Companion, first published in the late 19th century, set out the principles for formulating mixed drinks still adhered to today.

It reads: “As a general rule, shaved ice should be used when spirits form the principal ingredient of the drink, and no water is employed. When eggs, mild, wine, vermouth, seltzer or other mineral waters are used ... it is better to use small lumps of ice ... ”

Earlier this year, faecal bacteria was found in samples of iced drinks from Costa, Starbucks, and Caffe Nero.