British retailers took £114bn in the whole of 2015, up a 11% on the year before. A whopping 21% (£24bn) of that spend took place over Christmas, with £4.3bn spent on Black Friday weekend.

An American phenomenon, Black Friday was virtually non-existent in the United Kingdom in 2012. It’s the first Friday after November’s Thanksgiving and unofficially marks the start of the Christmas shopping season.

Since 2013 Black Friday sales revenue has grown at least 20% year on year. In comparison the UK’s online shopping spend has been growing at a steady 11% for several years and looks to match that trend this year.

With the current growth trends in mind, gadget insurance company Row.co.uk estimates that UK Black Friday sales will represent 47% of annual online sales by 2020. In pounds, that’s an eye-watering £81.1bn to be spent on one day alone. Annual online sales at the same point in time could be as high as £172.9bn.

Online retail giant Amazon said in 2015 that it sold more than 7.4 million items at a rate of around 86 items per second. The vast majority of purchases are for electronics and gadgets, mainly TVs, tablets, laptops and mobile phones.

With the British Black Friday spend now in the billions, it is officially the UK’s biggest shopping day and that doesn’t seem to be changing any time soon. Experts predict that £733 million was spent on Manic Monday in 2015, the first Monday in December, followed by £728 million on Christmas Day, £856 million on Boxing Day and £638 million on New Year’s Day.

“Several million mobile phones were purchased last year on Black Friday, with Carphone Warehouse alone claiming a 182% increase in handset sales”, a spokesperson for Row.co.uk said.

“There’s no signs that these sales will slow down. If you do take advantage of the great holiday savings to get your hands on the new iPhone 7, Galaxy S7 or Xperia XZ, do consider getting insurance from the smaller niche insurers like Row.co.uk, rather than accepting the network’s cover which can cost up to 80% more.”

Some experts now believe that the popularity of the Black Friday shopping weekend will phase out the traditional Boxing Day sales events.