But the escalation of this into a week-long discount frenzy makes no sense. It's not as if Brits are taking the day off after Thanksgiving. For non-food retailers, the fourth quarter can account for almost half of annual profits, so selling goods they would have probably shifted anyway, but at a reduced price, is pointless. Retail margins aren't exactly bloated in the first place.

In the age of online retail there's even less rationale for offering discounts to lure people into shops. Last year customers turned away from what had become "Black Eye Friday," with battles in shops for cut price TVs.

Blanket discounts invariably means best sellers move faster. But returns can be up to 50 percent, as people buying for themselves purchase several sizes of a garment to work out the best fit at home, and return the rest over the next three to four weeks.

The time it takes to get stock back on the shelves or available online means they won't be there before Christmas, and will end up in bargain bins after the holiday. That's a big loss of potential profit.

This year, a band of retailers have decided to ditch Black Friday altogether. These include Wal-Mart Stores Inc.'s Asda, an early adopter of the event. About 25 percent fewer chains are participating as of the start of this week, according to Richard Hyman, an independent retail analyst.

But some retailers are going full-throttle, as the threat from Amazon hasn't gone away -- and Gadfly has argued that the period may even represent an opportunity to challenge the giant. Dixons Carphone Plc and J. Sainsbury Plc's Argos all plan for the event long in advance and draw on the support of their big suppliers to provide discounts. Tesco Plc, Britain's biggest retailer, may do the same.

Delivering the goods in Somerfield — Photo: Sludgegulper

Tesco's an example of the cost of Black Friday -- it wants to double profit margins by 2020, and given that they're notoriously thin in categories such as electricals, the mark-downs are still probably ones it could do without.

And even in the U.S., there's already evidence that the event -- at least in physical stores -- has its limits. American electronics, apparel and toy retailers have little choice about whether they should join in -- 15 percent of holiday sales occur during Thanksgiving week, according to the National Retail Federation.

But a recent move to open on Thanksgiving Day didn't make sense for a number of retailers, who weren't attracting the crowds to justify keeping their stores open. Costco Wholesale Corp., Nordstrom Inc. and T.J. Maxx parent TJX Cos. Inc. won't open on Thanksgiving Day. People can order online, anyway.

Black Friday aside, Christmas is likely to be a decent one for U.K. retailers. Neither Brexit nor faster inflation has really hit the shops yet. In fact, the prospect that food and fashion prices could rise next year -- they could climb up to 5 percent -- may encourage some shoppers to buy now before prices go up later.

Conditions in Britain will undoubtedly be more difficult in 2017. So if retailers haven't got their addiction to the discounting drug under control this Black Friday, they need to go into rehab in time for next year.