Thousands of commuters faced yet more chaos today as people took to the roads to avoid the Tube strike.
An AA Roadwatch spokesman said the rush hour was "horrendous", with sections of the M25 brought to a virtual standstill.
The spokesman said: "We definitely had evidence of more cars on the road than normal because of the strike.
"Traffic is flowing but it is very heavy because of the tube problems. Today is not a good day for travelling by road."
Delays on the roads were made worse by flooding caused by heavy rain overnight.
A number of minor roads were closed and police urged motorists only to make essential journeys.
Train operator Connex said that rail services in and out of Brighton and Hove were not affected.
Less than half of London Underground trains were running today after drivers' union Aslef called the 24-hour strike yesterday evening.
In the capital, commuter misery boiled over and triggered a string of fights in bus queues. Extra police were called in.
A spokesman for the City of London force said: "People have been falling out with people who have failed to observe the queue system."
By 11.30am there were no trains running on the Circle, District, East London, Hammersmith and City, Northern or Waterloo and City lines.
Limited services were in place on the Bakerloo, Central, Jubilee, Metropolitan, Piccadilly and Victoria lines.
A London Transport spokeswoman said the effects of the strike could last beyond the 5.30pm deadline but services should return to normal tomorrow.
She said: "We are sorry that people are having such a rotten day. We are doing our best but it has to be done safely."
Two further tube strikes have been planned, one for next Monday and the other for the following Monday.
ASLEF, which represents 80 per cent of tube train drivers, called the strike over the Government's public-private partnership proposals it fears could threaten safety.
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