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The heaviest snowfall in 20 years has closed thousands of schools and caused transport chaos up the eastern side of Britain, with London and the surrounding areas the hardest hit.

Six million bus passengers were left in the lurch as all London's bus services were halted because of dangerous driving conditions, and every Tube line except the Victoria line was at least partially suspended.

Many mainline commuter rail services were also cancelled or seriously delayed, and flights at London's airports were decimated, with both of Heathrow's runways shut, Luton and London City closed, and Gatwick and Stansted flights subject to delays and short-notice cancellations.

Millions of commuters stayed at home rather than brave the conditions, as an estimated one in five people either worked from home or took the day off, costing industry hundreds of millions of pounds.

Meanwhile Westminster council in central London issued a statement that many of its schools would remain closed because too many teachers could not get to work, a message echoed by schools in Kent, East and West Sussex, Hampshire, Essex, Cambridgeshire, Birmingham, and West and North Yorkshire. In Surrey, every school was shut.

Many courts were closed as lawyers, witnesses and jurors were unable to turn up, and London Ambulance Service said it would only respond to “life-threatening calls” as the heavy snow and wintry weather meant it was under “severe pressure” and had received more than 650 calls between midnight and 7am today.

The South East of England and the Pennines bore the brunt of the snowfall which began yesterday afternoon, with some of the hardest-hit areas reporting up to 1ft of snow. By the morning the heavy showers had extended as far north as southern Scotland.

Forecasters are predicting that during the rest of the day and tomorrow the snow will continue to extend northwards and westwards across the UK, with a wave of even heavier falls due to reach Britain on easterly winds this afternoon.

"The South West has escaped the worst of the snow, but we could see another 10cm in Greater London over the next 24 hours, and even more than that in Yorkshire and the Pennines," said a spokeswoman for the Meteo forecasting group.

A spokesman for Transport for London said: "Heavy snowfall across the London area last night has severely disrupted transport services and further snow is forecast throughout Monday. The advice is to check before you travel, expect disruption and if your journey is necessary then allow more time for your journey.

"The biggest difficulty today is the road conditions which are extremely dangerous and drivers should take extreme care."