Tens of thousands of rail passengers in the south east are facing a week of chaos with severe disruption to some of the busiest commuter routes from Sussex and Kent into London.
Half of the platforms at London Bridge are closed all week to allow for a key part of the £6.5 billion Thameslink project.
Well passengers told us today it meant journey times doubling from key commuting places like Brighton, Horsham and much of the south coast.
Our Transport Correspondent Mike Pearse has been speaking to them and was this afternoon given exclusive access to see the work.
There are demands for a better deal for Kent rail commuters after it emerged they are paying 10% more than train passengers in other counties.
The leader of Kent County Council Paul Carter is calling on MPs to back a campaign for a "fairer deal for commuters".
He believes that commuters into London paid 10% above those from other counties, putting people off moving to East Kent regeneration areas.
The county council has called on the Government to ensure fairer prices, a move which has been backed by Canterbury MP Julian Brazier.
David Cameron described travel disruption caused by the Underground strike in the capital as "unacceptable" on Twitter.
It's unacceptable that millions of people are having their lives disrupted by today's Tube strike in London.
Thousands of staff and volunteers are working hard to keep the capital working during the "pointless" Tube strike, London Underground said.
TfL said the Victoria line was now running fully with the Central line running to Holborn and the Jubilee line running through from Wembley Park to Stratford.
London Underground managing director Mike Brown said:
Thousands of staff and volunteers are working hard this morning to keep London working and our customers informed in the face of this pointless strike.
More London Underground staff have come to work this morning than during the strike back in February, and a record number of London buses are operating.
A Transport for London spokesman said the RMT could not "claim a shut down in any sense of the word."
Passengers formed long queues in London Bridge underground station on the first morning of the Tube strike.
Commuters have been told to expect severe disruption, with TfL advising passengers to plan ahead.
A 48-hour Tube strike has created "total chaos" for Londoners just trying to get to work, one commuter has said.
Emily Toner told ITV London that she was forced to hire a Boris bike because of the crowds at Liverpool Street station:
When arriving at Liverpool Street at the Tube, I discovered the gates were still not open so I resorted to using a Boris bike to get into work.
Total chaos has been caused to good people just trying to get to work.
Commuters have reported having to wait a long time for black cabs at Paddington station this morning.
Staff at the station warned passengers to expect lengthy queues yesterday.