Mourners travelling to the Queen’s funeral could miss the event after damaged overhead wires blocked all rail lines between Slough and London Paddington.
It means likely delays for people travelling from Reading or Heathrow Airport. Great Western Railway (GWR), Heathrow Express and the Elizabeth line are all affected.
National Rail Enquiries said “major disruption” was likely until the end of the day, with potential cancellations and delays of up to 90 minutes.
Live – Dignitaries arriving for funeral – as all public viewing areas for procession already full
People are being advised to instead use South Western Railway services from Reading to London Waterloo.
However, officials have said all public viewing areas on the funeral procession route are already full ahead of the start of the funeral at 11am.
Passengers on a GWR train bound for Paddington were told over the tannoy: “My sincerest apologies for the delays on such an important day for the country.”
The rail problems are being caused by damage to the electric cables at Hayes and Harlington, towards the edge of west London.
Lines between Reading and Newbury are also closed after a person was hit by a train, meaning GWR trains are being diverted and again delaying journeys to the capital.
Travellers on GWR can use their ticket on Chiltern Railways, London Underground, or Southern.
People on the Elizabeth line can use their ticket on the Tube, London buses, First Berkshire between Slough and Reading, and on South Western Railway between Waterloo and Reading.