Major signalling problems have sparked a "meltdown" at Paddington station as commuters face "carnage" at Euston following a landslide.
Commuters have been urged to avoid the station this evening and travel tomorrow if possible after flooding and a power failure caused signalling problems.
Great Western Railway services and trains to and from Heathrow Airport have been cancelled or severely delayed.
Frustrated travellers took to Twitter to discuss the situation.
One user said there was “a lot of anger at the station”.
Another wrote: “Avoid the hellhole that is Paddington station. 90 mins to get on a train. Trying to escape London.”
Chloe Sands said: "Think it's really inconsiderate that Paddington station has a meltdown the day I come to London tbh, didn't anyone let it know.”
Commuters suffered travel chaos earlier today when a packed train was derailed by a landslide, the M25 was shut by flooding and lightning closed the rail line to Stansted airport as storms lashed the south east.
Torrential rain and thunderstorms caused disruption so severe that passengers were advised not to travel “unless absolutely necessary” as the transport network struggled to cope.
Cancellations and delays were due to last all day, with major problems at Euston, Liverpool Street, Paddington and Waterloo.
The derailment happened between Watford Junction and Milton Keynes around 7am after flooding caused a landslide onto the tracks, closing the West Coast Main Line for a period.
This evening commuters described Euston as "carnage" as pictures emerged of hundreds of people crammed into the station's concourse.
Tube strikes on the Circle and Hammersmith and City Lines caused further headaches for Londoners.
Images showed of crowds of travellers waiting outside Victoria station during rush hour.
A spokesman for GWR said: “Due to major signalling problems at London Paddington, services to and from London Paddington are severely disrupted.
“Customers with non-essential journeys are advised not to travel.
“Customers with tickets for today's travel, can travel tomorrow (Saturday 17th September).
“For those journeys at that are essential; South West Trains, Chiltern Railway, Cross Country Trains, TfL Buses and London Underground are all accepting GWR Tickets.
“Significant delays and short notice alterations to journeys can be expected.”
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