Travel chaos prevented thousands from reaching work across Britain on Monday and 140,000 homes were without electricity as the St Jude storm unleashed winds of almost 100 mph across swathes of the country.

At least 100 trees have fallen across railway lines in the south east, Network Rail said.

The Met Office issued an "amber" wind warning for southern England and south Wales, the third highest in a four-level scale.

The rush hour was chaotic in London after train companies First Capital Connect, C2C, Greater Anglia, Southern and Gatwick Express services cancelled all their early morning services, predicting the first trains would not run until after 9:00 am.

In the heart of London, a crane collapsed on to the roof of the Cabinet Office, causing the closure of Whitehall between Parliament Square and Horse Guards Avenue.

London Mayor Boris Johnson will chair an emergency resilience meeting involving all emergency services and relevant agencies later this morning.

Tracy Elsey, communications manager for UK Power Networks, told the BBC Radio 4 Today programme: "We have got close to 140,000 people without power at the moment.

"In our East of England region, which goes from Essex up to the North Norfolk coast, we have seen a huge rise in reported power cuts. We have got 100,000 properties off power in the East."

Scottish and Southern Energy (SSE) said more than 38,000 customers were left without power in Cornwall, Devon and Somerset, while Western Power reported more than 3,800 power cuts in the same areas, Downing Street said.

Police said at least 125 trees were down across roads in Sussex by 6.30am, and Kent Police said at least 70 trees had been blown down across the county.

Transport for London (TfL) said there was disruption to six Underground lines due to debris from the storm on the tracks.

The Bakerloo, Central, Jubilee, Metropolitan, Northern and Piccadilly lines were all partially closed while workers removed fallen trees and other obstructions, a TfL spokesman said.

The Environment Agency has 137 flood alerts in place across England and Wales, warning people to be prepared, and 13 flood warnings, with 12 in the South West.

Winds of up to 80mph have been reported, while a gust of 99 mph was recorded by the Met Office at the Isle of Wight at 5 am.

Major airports also warned of disruption to flights with London hub Heathrow expecting approximately 30 cancellations.

Cross-channel train service Eurostar said it would not be running trains on Monday until 7:00 am, meaning delays to early services.

Several ferry operators said they had cancelled some cross-Channel services and Irish Sea crossings.

Forecaster Helen Chivers told AFP the expected damage was likely to be comparable with a storm seen in October 2002.

Martin Young, chief forecaster at the Met Office, said: "While this is a major storm for the UK, we don't currently expect winds to be as strong as those seen in the 'Great Storm' of 1987 or the 'Burns Day storm' of 1990.

"We could see some uprooted trees or other damage from the winds and there's a chance of some surface water flooding from the rainfall -- all of which could lead to some disruption."

The storm has been named St Jude after the patron saint of lost causes, whose feast day is on Monday.