• Outage saw all Southern train services unable to run through Victoria
• 904 passengers evacuated from one train
• One train was stuck for six hours before being towed into London
• Gatwick Express service temporarily suspended
• Medics and firefighters boarded trains to hand out bottles of water
• Delays expected for the rest of the day
Many Clapham Junction and Victoria Station services are operating with severe delays Thursday evening rush hour after a major power cut near Wandsworth Common.
Some passengers had to be rescued by police and firefighters after becoming stranded in sweltering temperatures for hours.
Water had to be handed out to stricken travellers, some of whom were still waiting to reach London more than five hours after boarding their train.
Our services are severally disrupted due to the incident at #ClaphamJunction. Pls see feed below for Ticket acceptance with other companies.— SouthernRailUK (@SouthernRailUK) April 30, 2015
— SouthernRailUK (@SouthernRailUK) April 30, 2015
The problem, which was set to cause disruption into the evening, was compounded by the fact that it affected Clapham Junction in south London - the UK's busiest interchange station.
One passenger had to be treated by ambulance staff on one of the stationary trains, while firefighters used a short-extension ladder to evacuate travellers from one held-up service.
British Transport Police (BTP) reported evacuating 904 passengers from one train, while travellers on another stricken service were waiting for a tow.
Passengers spoke of "nightmare" conditions at Clapham Junction.
No Southern train company trains were able to get in or out of London's Victoria station and there was no service on the Gatwick Express.
Passengers heading for London from southern England found they had to get off well short of their destination and travel in on other rail routes.
The unfortunate ones got stuck on trains unable to get through Clapham Junction.
One of the worst-affected trains was the 6.56am from Brighton which should have got into Victoria at 8.15am.
Shortly after noon the train was still stuck near Clapham.
One of its passengers student Hannah Phillips, 20, from Eastbourne, East Sussex, said: "I was lucky that I was carrying a bottle of water with me as it was getting very hot on the train.
"This is probably the worst train journey I've experienced."
Another passenger on the held-up Brighton train was Ben Goode. He tweeted: "This is a shambles."
Also on the train was Anna Roberts, a Press Association journalist.
Power failure causes rail chaos in south London #VictoriaApril 30, 2015
She said: "Police and paramedics boarded our train because there is no air conditioning.
"They said they were bringing water but not enough for everyone to have one bottle each. Eventually we got water in plastic containers which we are passing around the carriage.
"We were told that was all that was available. With the power off, it's like an oven in here.
"Police have said it's too dangerous to walk down the track."
The problem struck between Wandsworth Common and Clapham Junction in the middle of the morning rush hour.
FiniasFinn tweeted: "Clapham Junction is the worst station ever. I realise it's chaos but no staff helping and being arrogant is not a help."
Thomas Michael Jules wrote: "Avoid Clapham Junction today people! Mayhem!!"
A person called Precious tweeted: "Complete chaos at Clapham Junction this morning as trains are delayed left, right and centre. What a nightmare!"
A Network Rail spokesman said: "A major power supply problem between Clapham and Wandsworth Common has disrupted Southern train services into London Victoria this morning.
"Engineers are on site and we aim to resume services as quickly as possible.
Avoid Clapham junction today people! Mayhem!!— Thomas Michael Jules (@ThomasJules81) April 30, 2015
"Tickets are valid on all other routes into London and Southern passengers are advised to avoid travelling through Clapham Junction, which is very busy.
"South West Trains services to and from Waterloo via Clapham Junction are unaffected."
Those on the stricken 6.56am train from Brighton were finally towed to Wandsworth in south London, arriving shortly before 1pm.
National Rail information said that problems with the conductor rail between Wandsworth Common and Clapham Junction had caused damage to a number of trains.
Once the trains had been moved repairs were likely to take up to three hours. Passengers were advised to avoid using Victoria station.
Shortly after 1pm Gatwick Express trains began running again but with delays. A spokesman for Gatwick Airport said that there had been no reports of missed flights so far because of the incident. He added that the Gatwick Express was now running again and that there are also alternative routes to the airport.
Ev1s so miserable @ #ClaphamJunction
Figure i'll cheer em up, ask them about summer.
"Are YOU beach body ready?"
Stay tuned for results.— Aid Thompsin (@AidThompsin) April 30, 2015
The train I've been stranded on for nearly six hours started moving! Everyone cheered! It stopped immediately #ClaphamJunction— Anna Roberts (@journoannie) April 30, 2015
Mick Cash, general secretary of the RMT rail union, said: "Chaos at major London railway stations is now a matter of course as the reality of trying to shove growing passenger numbers into an overstretched and understaffed network hits home.
"It is about time Network Rail properly valued those staff who are battling to keep services moving that are routinely running right on the edge.
"The hundreds of millions of pounds bled from our railways by privatisation would have gone a long way to building in the capacity and reliability that passengers rightly demand."
A spokesman for the Southern train company said: "We would like to apologise to our passengers who have been disrupted by today's events. We'd also like to thank them for their patience and understanding during some very challenging circumstances.
'Avoid Victoria and London Bridge tonight' passengers warned http://t.co/eainZlENbp— The London Girl (@iamtheldngirl) April 30, 2015
"We currently have a very limited service into and out of Victoria while Network Rail repairs the power supply rail and we are advising passengers to avoid using Victoria if at all possible.
"We expect there to be disruption to this evening's peak, with delays, cancellations and short-notice alterations to services as trains and train crews will be out of place."
Network Rail (NR) urged evening rush-hour passengers to consider starting their journeys either earlier or later than normal and to check with websites and social media sites before travelling.
An NR spokesman added that Southern services to and from London Bridge would also be affected by possible delays, while Victoria station was likely to be very busy, with a queuing system in place for services from platforms 15-19.