There are severe delays on services in and out of London Liverpool Street this morning, due to an earlier signalling fault.
Greater Anglia, London Overground and Stansted Express services are affected.
"The fault with the signalling system at London Liverpool Street earlier this morning has now been rectified. Trains running to and from London Liverpool Street may still be cancelled, or delayed by up to 30 minutes, whilst the service recovers," said National Rail.
There are currently no London Overground services between Liverpool Street and Hackney Downs.
Disruption is expected to continue until approximately 10am.