Millions of bargain-hunters have descended on the high street for the Boxing Day sales - with wealthy Chinese tourists helping to fuel bumper takings.
But there were reports of violent clashes at some stores, and shoppers fled "for their lives" after a fight believed to involve a machete erupted among youths at a shopping centre in Bromley, south London.
Elsewhere shoppers said stores were like a "madhouse" as bargain-hunters set about getting the best deals.
Crowds started queuing from 1am on Saturday as they braved the wind and rain to get their hands on the best deals.
Experts predicted that 22 million people would have hit the stores, spending as much as £3.74 billion.
Selfridges had its most successful-ever first hour of trade, taking more than £2 million between 9am and 10am across its stores.
Jace Tyrrell, chief executive of New West End Company, which represents retailers in Bond Street, Regent Street and Oxford Street, said wealthy foreign tourists were fuelling bumper sales.
He told the Press Association: "We are in the west end, which is a huge international draw, so we see a lot of international shoppers here - 50% of our shoppers are tourists, particularly from China, the Middle East and the US, and they probably spend about four or five times the amount of a UK shopper."
He said some shoppers had brought along suitcases to stuff with bargains and they were expecting £100 million to go through the tills in the three days beginning Boxing Day.
He said: "£100 million is the target and we are in line to do that as forecast.
"We are seeing more Chinese here than ever before, which is good news for our retailers, and they are spending a healthy amount of money, which is good for our stores."
Selfridges said it is on course to break sales records across its four stores and online.
The first bargain-hunters through the door headed straight for the luxury fashion section, with designs by Valentino, Erdem and Victoria Beckham the first off the shelves.
The store reported massive growth online, and Christmas Day online purchases have doubled compared to last year, Selfridges said.
Harrods in Knightsbridge, central London, saw one of its biggest-ever queues, which ran around the corner of the store.
The department store expects more than one million customers to come through its doors during the four-week winter sale.
Sally Erwin, a shopper from the US at Selfridges in Oxford Street, said: "This is really a madhouse compared to the United States. I don't think we have this at all.
"I think we have queues and everything, but we don't have it like this, it is kind of mobbish."
Daniel Graham, from Australia, was out shopping with friends who were hoping to snap up a bargain at Selfridges.
He said: "It's a bit mental, there are a lot of people, a few fights. This lady was trying to push in, and this person wasn't taking it, so they got security."
John Lewis launched its sale online, although its shops remained closed, and officials said its sale has got off to a "strong start" after launching on Christmas Eve at 5pm.
In its first hour of online trading sales were up 17.7% on last year, with the Apple sports watch, goose down pillows and a KitchenAid mixer among its most popular sellers.