Britons rushed to stores on Monday to stock up for Christmas after stricter pandemic rules meant last-minute changes to their plans and as countries closed borders to Britain, raising fears of supply shortages.
On traditionally one of the busiest shopping days of the year, large queues snaked around supermarkets across London.
Many shoppers were buying traditional Christmas fare, or adapting it after Prime Minister Boris Johnson imposed stricter measures from Sunday which have stopped many families meeting up and pushed people to rush to buy food for their own gatherings.
"Sunday was exceptionally busy - today has gone bananas," said one supermarket manager.
At Waitrose in Clapham, many shoppers had planned to leave London to see family for the festive period but were now stocking up for a Christmas in the capital.
Meat and milk were sold out in some supermarkets but traditional panic buying targets such as baked beans and pasta were in good supply.
Gaps will start to appear on British supermarket shelves within days if transport ties with mainland Europe are not quickly restored, the UK's two biggest grocers warned on Monday.
Freight from France is being disrupted as part of a wider suspension of travel links with Britain to try to curb a new faster spreading strain of COVID-19.
The French government has closed its border to arrivals from Britain for 48 hours, which means no lorries can leave the English port of Dover, the main gateway to Europe.
Market leader Tesco and No. 2 player Sainsbury's both said if the disruption continued food supplies would be impacted.
"If nothing changes, we will start to see gaps over the coming days on lettuce, some salad leaves, cauliflowers, broccoli and citrus fruit," said Sainsbury's.
Tesco highlighted the same products, apart from broccoli.
Johnson's spokesman said supply chains were resilient, adding that French President Emmanuel Macron was keen to resolve the crisis within hours.
"It remains the position that people should shop normally," the spokesman said.
Despite the rush on Monday, retailers said they had not seen any major changes in customer buying behaviour.
They said it was in line with what they expected for Christmas week, pointing out that 21 December is always one of the busiest days on the retail calendar.
“We have plenty of food for Christmas available in stores," Tesco said.
"We’ve been building our stockholding of key products ahead of the Christmas peak and are working closely with our hauliers and suppliers to continue the supply of goods into our stores."
Sainsbury's said all products for "the Great British Christmas lunch" were already in the country and it had plentiful supplies.
All supermarket groups are, however, seeking to source more from Britain and looking into alternative transport for produce sourced from Europe, including using ferries directly from Spain and increasing stock from the Netherlands.
Britain's Food and Drink Federation warned the crisis had the potential to cause serious disruption to Christmas fresh food supplies and exports of food and drink.
"Continental truckers will not want to travel here if they have a real fear of getting marooned," it said.
The British Retail Consortium, which groups more than 170 major retailers, said any prolonged French border closure would be a problem in the final days before a Brexit transition period with the European Union ends.
That deadline meant freight transport was running at near record levels as British companies stockpiled.
Industries beyond food and consumer goods also fear disruption from even a relatively short travel ban.
"Once all the vehicles are out of place it will take time to rebalance the system," an aerospace executive said.
