Black Friday: On Friday, the UK's largest retailers are expecting thousands of people to descend on their stores to pick up a bargain

Black Friday, the big sales day in the US that follows the Thanksgiving holiday, is being adopted by more and more shops in the UK.

It was brought over by online store Amazon four years ago as internet shoppers noticed the US got the best deals.

Most offers will be on electrical goods such as TVs, tablets, kitchen gadgets and audio hardware, he says, as electricals are often where shops can get the best deals from suppliers.

In the UK, Black Friday has been led by "the three As," says Mr Bubb: Amazon, Apple and Wal-Mart's Asda.

And this year is likely to see the biggest Black Friday sales yet as more people know about the event and more shops participate, say analysts.

Tesco says it expects Black Friday to beat Boxing Day sales in 2014 as it prepares discounts of as much as 70%. Its 24-hour stores will begin selling a minute after midnight, and more staff may be laid on in some areas.

This year rival Sainsbury's will enter the fray with 485 stores taking part, while Asda says it will be using the buying power of its US-based owner Wal-Mart to bring more bargains to UK shoppers.

Department store John Lewis says it will put on about 100 deals and will add staff at its main distribution centre and in stores.

"Following steady growth over the last few years, Black Friday really emerged in the UK in 2013, when we saw the day break our previous records for a single day's online trade," says Mark Lewis, online director at John Lewis.

According to a Visa estimate, spending on Black Friday in the UK will be up 22% on last year with £1m spent on its cards every three minutes on the day.

A product of this Christmas sale in November is lengthening the shopping season, says Jacques de Cock of the London School of Marketing.

"Ultimately, customers only have a finite pot of money," he says, but purchases made sooner rather than later mean "people will forget" what they've spent, so shops are trying to lengthen the shopping season.

Another reason for this early sales event is its part in the game of chicken played between shops and shoppers, says Clare Rayner, founder of the Support for Independent Retail campaign.

Customers have money to spend and want to buy gifts, which the retailers know

On the other side of the coin, shops need the festive period to be a profitable one to keep shareholders happy or merely to survive, which consumers know.

This has previously meant customers being prepared to wait and wait for the best deals to arrive, knowing shops will eventually blink and offer them a bargain for fear of losing their custom to a competitor.

Now shops are adopting this American tradition of a pre-Christmas sale period to capture those sales.