Elizabeth Line and Heathrow Express trains are unable to run to part of Heathrow Airport after a tunnel was closed over safety concerns.
Trains are unable to run to Heathrow Terminal 5 due to faulty tunnel ventilation, Transport for London has warned.
There is no service between Heathrow Terminals 2 & 3 and Heathrow Terminal 5 and disruption is expected until the end of the day.
Meanwhile lines have reopened on the London Overground between Clapham Junction and Willesden Junction after disruption due to an earlier faulty train. There is now a good service on the Overground.
Earlier on Thursday, Eurostar trains in and out of London St Pancras International were delayed by up to two hours due to a power cut.
