Travellers are being warned they face disruption to and from a major London railway hub for much of Wednesday.
Trains are unable to run between London Paddington and Slough or Heathrow Airport after overhead electric wires were “severely” damaged at Ealing on Tuesday night.
Many trains became stranded between Paddington and Reading due to a loss of power supply.
Network Rail said it expected to open two of the four train lines by midday, but warned disruption would last until the end of the day.
Great Western Railway (GWR) added that a reduced timetable would impact most mainline routes to and from Paddington.
The operator said: “Owing to the extent of the damage, no trains are expected to be able to operate between London Paddington and Hayes & Harlington in either direction for much of Wednesday.
“As a result, GWR, TfL Rail and Heathrow Express will not be operating a train service between London Paddington, Hayes & Harlington or Slough until such time as repairs have been completed.”
It added: “If you are travelling from London beyond Reading please do not go to London Paddington but instead travel straight to either London Waterloo, London Marylebone or London Euston depending upon your ultimate destination.”
GWR staff wheeled a trolley on to the Paddington concourse at around 8.30am to give away free tea, coffee and biscuits to frustrated commuters.
One member of staff said it was to try and “make things a bit better” for travellers.
The disruption comes after commuters faced major delays on Tuesday evening as electricity supply problems caused delays and cancellations on a number of busy routes in and out of London.
Southern, Southeastern, Thameslink and Gatwick Express were all reporting cancellations and delays of up to 45 minutes.