Hundreds of thousands of commuters on one of London's busiest rail networks have been warned to expect two days of travel chaos as the bitter guards' strike spreads to new lines.
South Western Railway, which operates trains between Waterloo and Surrey, will on Wednesday be hit for the first time when RMT union members stage a 48-hour walkout.
The union is involved in a long-running battle with rail industry bosses to protect the traditional role of guards and conductors on passengers trains.
A third of SWR services are expected to be disrupted with commuters facing rush hour delays, cancellations and overcrowding.
The dispute will also affect some Southern and Greater Anglia trains.
SWR managers accused the RMT of calling an "unnecessary" strike because the company has no plans to abolish the role of guards on its trains.
'We have repeatedly assured the RMT that we plan to keep two safety-trained employees on our trains," a SWR spokesperson said.
"No one will lose their job. We have been very clear that we are guaranteeing the jobs, salaries and terms and conditions of Guards."
RMT general secretary Mick Cash said the strikes were about rail safety "pure and simple".
"Only this week at the Wimbledon derailment it was the guard on that train who safely evacuated 300 passengers in an emergency situation," he said.
"Those are the same guards that South Western Railway used to call legends and who they now want to throw off their trains."