Updated August 31, 2021 at 9:50 AM ET

On a recent afternoon outside a McDonald's in central London, customer Alon Williams considers indulging in a milkshake, likely chocolate or vanilla.

He is about to be disappointed. The American fast food chain has been out of milkshakes for most of the week.

When a familiar staple on the menu is suddenly missing, it's a big deal.

"It's a real shame you can't get a milkshake if you need one because McDonald's are the best at milkshakes," Williams said.

Last week, a well-known chicken restaurant chain, Nando's, ran out of chicken and closed 50 U.K. stores. And in recent months, supermarkets and gas stations have reported supply problems, too.

This isn't the fault of the cows or the chickens. Rather, a lack of truckers is responsible.

Many European truck drivers left the U.K. after Brexit

Many companies in Britain have found it impossible to get supplies recently, after scores of European truck drivers left the U.K. in the aftermath of Brexit. And the COVID-19 pandemic has only made things worse, creating new barriers to entry for aspiring drivers who want to join the industry.

Tom Holder of the British Retail Consortium says there's a shortage of around 90,000 heavy goods vehicles drivers. They transport food and other items from farms and factories to warehouses and distribution centers to shops, he said.

"This shortage means that there is some deliveries that simply aren't able to happen, or the cost of deliveries is going up," Holder said.

Experts say one of the causes for this shortfall is that Brexit and the pandemic that prevented people from getting new licenses.

About 45,000 people were unable to get a test to drive a truck in the U.K. since the pandemic started, according to Alex Veitch, who oversees public policy at trade body Logistics U.K. Tens of thousands of European drivers also left the country, he added.

"What would've been a solvable problem if it was just Brexit have become a very troubling and difficult-to-solve problem because of coronavirus," Veitch says.

The drivers, like Polish trucker Tomasz Orynski, blame pay and conditions.

"For many years, nothing was done to improve drivers' lives because Britain relied on cheap drivers from Eastern Europe," says Orynski, who lives in Scotland.

He said he's seen Polish truck drivers return to Poland because they can have a better life there.

Last month, the U.K. introduced a temporary measure allowing truckers to work longer hours. Officials also say they will consider plans to streamline licensing, boost testing capacity and improve working conditions.

Note: McDonald's is among NPR's financial supporters.

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