IT’S COME TO THIS: Black day? Guinness runs dry in UK pubs amid online craze.

At her London pub, landlady Kate Davidson has taken to issuing Guinness ration cards, but still the beer has run out amid a UK shortage of Ireland’s national drink.

Bars across Britain, even Irish ones, have reported limited supplies of the black stuff since Guinness owner Diageo announced earlier this month that it was experiencing “exceptional consumer demand”.

“I’m a bit shocked because it’s Christmas,” said Davidson, co-owner of the Old Ivy House, where an empty upside down Guinness glass signalled that its tap had run dry.

“I wouldn’t have expected them to run out at this time of year,” the 42-year-old told AFP at the cosy boozer in the Clerkenwell area of central London.

A number of factors have meant that Diageo has become a victim of its own success.

Earlier this year, Diageo chief executive Debra Crew said Guinness consumption was up 24 percent among women, as the company shifts its marketing strategy to attract new consumers.

So-called “Guinnfluencers” online — including Kim Kardashian, who has posted a photo of herself with the beer on Instagram — have been credited with fuelling the stout’s appeal among Gen Z.

As P.J. O’Rourke famously wrote, “You can’t get good Chinese takeout in China and Cuban cigars are rationed in Cuba. That’s all you need to know about communism.” And now apparently, you can’t get Guiness in England.