London ? Westminster Abbey, Big Ben and St. Paul’s Cathedral were crowned in a picturesque white frosting.

On the streets of London Monday, the trademark red buses were idle. The Underground trains had ground to a halt. Colossal traffic jams clogged roads because of fender benders and more serious accidents. And commuters found themselves slogging through slushy sidewalks — often for miles.

The biggest snowfall to hit London in 18 years was hardly a blizzard, but it still shut down the city that beat back the Blitz.

It also raised a vexing question of why a predicted winter storm caught authorities so unprepared.

Transit officials had nearly a week to get ready, but they failed to keep things running normally in the capital, which was buried under more than four inches of snow overnight and another four inches in the afternoon.

“There’s no point in going to work today,” said office worker Caroline Samuel, 36, after waiting for an Underground train that never arrived. “I’m going home.”

All five of the capital’s airports briefly shut down — with nearly 800 flights canceled throughout the day and thousands of passengers stranded. An international flight skidded off a taxiway at Heathrow, causing no injuries.

The city’s extensive bus network was completely closed for most of the day and many trains simply didn’t run.

London’s Ambulance Service’s operations director Richard Webber said the bad weather had put the department under severe pressure, adding that it will respond only to calls from people with life-threatening injuries or illnesses.

Some people strapped on cross-country skis to get around; others spent the day sledding with their kids.

Problems extended to France and Ireland as well, with airports in both countries reporting numerous delays and cancellations and motorists facing icy hazards.