Commuters have been warned to expect disruption on Monday morning because of a 'major track fault' at London Liverpool Street station.
Greater Anglia said the fault would prevent trains from using some platforms, meaning alterations to some peak services.
Plans were due to be finalised this evening, but some services on the routes from Norwich, Ipswich, Harwich, Clacton, Braintree, Colchester, Chelmsford, Southminster and Southend to London were expected to be affected.
Off peak services are scheduled to run as normal.
If the alterations go ahead, ticket restrictions will be lifted and tickets from Great Eastern Main Line stations will also be valid on West Anglia services.
Network Rail engineers are working to fix the fault.
Customers are advised to check the Greater Anglia website www.greateranglia.co.uk later for details of any service alterations.
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