Tens of thousands of passengers hoping to travel to London for the state funeral of the Queen are stranded on trains after an overhead wire failure closed the main Great Western Railway line.
No trains are expected to run to and from London Paddington station to South Wales and the West of England for the rest of the day.
Engineers from Network Rail, which runs the infrastructure, are trying to repair the damage at Hayes & Harlington, near Heathrow airport.
A spokesperson for Network Rail said: “We are very sorry for the disruption which we expect to continue throughout the day.
“We are working hard to get services running as soon as possible and passengers are strongly advised to check before they travel.”
GWR initially said disruption would continue to 10am, but as that time passed the platforms at Paddington remained filled with empty trains.
Craig Spencer and his wife, from Pontypridd in South Wales, had walked to Paddington after queuing for 11 hours to pay their respects to the Queen at the lying-in-state.
“It was a good experience, but the rest of it has been a bit dire since.
“We were going to go to the funeral procession today, but everywhere is choc-a-bloc – totally full so you can’t get anywhere.
“We walked up from Hyde Park to the station only to find out that we can’t even get onto our train. Not very good at all.”
The couple were told they would not be able to get on any trains until 4pm.
As well as links to Bristol, Cardiff, Swansea, Oxford and Plymouth, airline passengers heading for Heathrow discovered they were unable to reach the airport except by taxi or a slow Tube journey.
Clare, a passenger from Newbury in Berkshire, abandoned her plan to fly on a work trip from London Heathrow to Dublin.
She said: “There were already delays and then I got to Reading and the train I was on was cancelled. I had to get a train then to Waterloo instead, then travel across London to Paddington, and then the Heathrow Express is cancelled anyway, so I won’t make it in time for my flight.”
GWR also said there were further problems on the main line from Cornwall, Devon and Somerset to the capital “due to a person hit by a train between Reading and Newbury”.
The 4am departure from Plymouth was running three-and-a-half hours late by the time it reached Newbury. It was due in to London at 7.16am. The 5.10am departure from Bristol Temple Meads, due in at 7.36am, reached Reading over three hours late, with the last leg of the journey to London cancelled.
Passengers emerging from the London Underground at Paddington station are being turned around and advised to go to Waterloo, where some trains are running to and from Reading.
Chiltern Railways, CrossCountry, Avanti West Coast and South Western Railway are all accepting GWR tickets for travel via any reasonable route.
Tonight’s Night Riviera sleeper train between Paddington and Penzance has been cancelled in both directions.
Daytime services on Tuesday could start later than usual.