Passengers were facing rush hour chaos at Euston after a day of delays, with some complaining of being stuck on trains for hours without food or water.
Multiple incidents, including overhead cables snapping, a points failure in the Wembley Central area and a person being hit by a train between Watford Junction and Euston, meant all lines were closed, said National Rail.
Trains to and from the station were being cancelled, delayed by up to 90 minutes or revised. Major disruption is expected until the end of the day Wednesday.
Earlier, hundreds of passengers had been left stuck on board affected services, with firefighters eventually managing to free people from one train after the live cables came down on the rails.
Some passengers were evacuated off trains that could not make it into the station and escorted along the rails to safety.
One fed-up passenger facing the rush hour chaos on Wednesday evening said: “Stuck at bloody Euston, in the hour I’ve been here just 4 trains have turned up.”
Another said: “Absolute carnage at Euston station… loads of trains cancelled including mine. Hardly any trains showing on the board”.
A third said: “Absolutely chaotic seats at London Euston where there are no services running other than those to Northampton.
“Other rail operators didn’t get the festive spirit memo and refusing to accept tickets, so only prospect to wait for completely unknown period of time for next service.”
Commuters reported being unable to board some services which did arrive in the station because there were too many people.
While others complained of a lack of information on departure boards that remained blank.
A spokesperson for Network Rail earlier said: “West Coast main line passengers are being warned of major delays after 25,000-volt overhead cables which power trains came down outside London Euston station.
“Network Rail engineers are racing to fix the damage to the essential web of wires which got caught on a passing train at 8.50am this morning.
“Teams have also been working to help passengers safely get off trains which had to be brought to a stop when the electric lines were forced to power down.
“The damage means no trains can currently serve platforms 1-7 at the major London terminus.
“Passengers are being advised to check www.nationalrail.co.uk with disruption expected for the whole of today.”
Passengers who were left stranded on trains earlier in the day also vented their frustrations.
One said online: “We’re stuck here since 8.45, no water, no air, nothing! Train jammed packed and only update we had was that we’ll off board in 20 min which was about 90min ago.”
Another said: “Absolute scenes at Euston - sold out train cancelled, all crammed on another sold out train.
“I am literally standing in the toilet. Open first class for gods sake, @AvantiWestCoast are the worst of the worst.
Another disgruntled commuter added: “300+ people waiting on a train outside Euston on 1 driver to move a train off a platform! how many meetings missed, how much revenue lost, all on one driver.
“And then there’s a queue of other trains behind us! Broken system.”
Among those caught up in the delays were former Labour spin doctor Alistair Campbell and Olympic marathon runner Scott Overall, both of whom tweeted about their experience during the disruption.