A major power failure on Tuesday heaped travel misery on thousands of South Western Railway commuters in the United Kingdom.

Passengers were already contending with 550 cancellations and delays as a result of the latest 24-hour walkout in a "summer of strikes" called by members of the National Union of Rail, Maritime and Transport Workers (RMT), one of Britain's fastest growing trade unions.

Then the fault between Haslemere and Guildford closed the main lines in both directions between Waterloo and Portsmouth. Services were cancelled, diverted or stopped short of their destinations throughout the peak hours.

South Western Railway (SWR) told stranded commuters trying to reach London that "until power has been restored to the track no trains are able to run through the affected area."

The rail company said it expected to operate only two thirds of its usual 1,700 trains Tuesday because of the walkout by guards in the long-running dispute over changes to their role and train driver-only operation.

However, it said fresh talks are "imminent." SWR will meet RMT leaders at Acas, the conciliation service, in the next 24 hours.

An SWR spokesman said, "We will do everything we can to make journeys as smooth as possible."

The RMT general secretary, Mick Cash, said guards were "standing firm" with their strike action. He said that documents obtained under Freedom of Information revealed the British government's advisors warned two years ago that driver-only trains are "toxic for disabled and older passengers."

Tuesday is the third of seven planned strikes. The rest will take place on the Saturdays of Aug. 4, 11 and 18, with a 48-hour strike on Friday, Aug. 31.

Angry passengers complained of severe delays and packed platforms and train carriages on Tuesday morning.

Photos posted on showed commuters crammed into train carriages and queues of people waiting to get onto already crowded trains.

One customer named Kat tweeted: "You're reduced service is making all trains overcrowded... I've been stood at Wandsworth Town for over an hour and haven't been able to get onto a train!"

The RMT union, which is organizing the strikes, said it was "angry and frustrated" after last-ditch talks with the rail operator failed to reach an agreement.

SWR described the outcome as "frustrating and disappointing" as it warned passengers of a reduced service across the network.

There will be no services at all from Leatherhead to Dorking, Surbiton to Hampton Court, Teddington to Shepperton and at Berrylands station.

Commuters hoping to use SWR services during the strikes have been advised to check before they travel.

A South Western Railway spokesperson said, "Passengers have suffered some additional disruption this morning due to a number of issues, the most disruptive of which were a major problem with the power supply on the Portsmouth line which meant we were unable to run trains until 06:30, and a member of depot staff going sick at short-notice which caused problems on the Reading line."

"We are sorry that these incidents have led to further disruption for our passengers," the spokesperson said. "Despite the RMT strike, we are still planning to run around two thirds of our services today and are providing extra carriages where possible to increase capacity, however trains will be busier than usual."