Boxing Day sales are expected to plummet as coronavirus restrictions have forced shops to close for large swathes of the UK.
By midday, footfall was down 60% across the UK compared with last year, according to retail experts Springboard, and shoppers are expected to spend £1 billion less, according to Barclaycard.
Strict measures in Scotland, Northern Ireland, Wales and Tier 4 restrictions for 43% of England's population meant non-essential shops were closed across the nation.
In scenes the chief executive of the New West End Company Jace Tyrell described as "heartbreaking", the London district was empty on Boxing Day for the first time since 1871.
Mr Tyrell, whose company represents 600 retail and leisure businesses, said the days around Christmas are usually "the key golden period" for sales but Tier 4 restrictions have had a "huge impact".
Coronavirus has cost the district 80% of its usual year-on-year sales, with £2 billion forecast to be lost during the Christmas period.
Footfall in Tier 4 regions of England fell by 77.3% compared with last year, and even in Tiers 2 and 3 areas where shops are open, footfall was down by 38.2% and 42.4% respectively, according to Springboard.
An estimated £2.7 billion will be spent by UK shoppers by the end of Boxing Day, and each consumer plans to spend an average of £162 online, according to research from Barclaycard, which sees nearly half of the nation's credit and debit card transactions.
This is down from last year's projection that one in four adults were expected to make the most of Boxing Day sales, spending an average of £186 each and a total of £3.7 billion.
Barclaycard said, based on their survey of 2,000 people, there are indications more people did their sales shopping online on Christmas Eve and Christmas Day due to a socially quieter festive period this year and Boxing Day sales are expected to be largely online too.
Rob Cameron, chief executive of Barclaycard Payments, said: "While high street footfall will be down, we're optimistic that an online shopping boost will give retailers a much-needed uplift as they head into the new year."
Diane Wehrle, insights director at Springboard, agreed that while the losses from reduced footfall will be offset a little by virtual "comfort-buying", for the majority of retailers "the sales they get online are much smaller than what they get in-store".
Mr Tyrell, who has worked in the West End for 20 years, added the damage goes beyond Boxing Day and businesses urgently need the Government to extend the business rates holiday due to end in April 2021, and to re-introduce tax-free shopping.
He said: "One of the biggest costs that retailers face particularly in hospitality is business rates, and they were very generous with the holidays last year which was so vital.
"But we need to know now if the Government is going to extend that holiday beyond April, otherwise we're going to see a collapse of hundreds of businesses in January, and that's tens of thousands of jobs, and the West End won't be immune from that."