Rail passengers are facing disruption to rush hour trains on Monday because of a "major track fault" at London's Liverpool Street station.
Greater Anglia said there would be some cancellations as well as a "slightly reduced service" running between the capital and Norfolk, Suffolk and Essex.
The train operating company announced the possibility of alterations at 4pm but only started revealing the changes at 10pm on Sunday.
In the absence of firm details, commuters had taken to Twitter to ask about their travel plans.
One replied: 'Still no revised timetable. GA you are the epitome of all that is wrong with train companies."
Others blamed Network Rail for the problems and singled out chief executive Mark Carne, who was awarded a CBE on Friday despite continuing rail chaos.
Greater Anglia, which is a joint venture between Dutch and Japanese firms, apologised to customers for any inconvenience and said Network Rail engineers are working to fix the problem.
"Due to a major track fault at London Liverpool Street station, preventing the operation of trains into some platforms, it is likely that there will be alterations to some Greater Anglia peak services on Monday 11 June," it said in its initial statement.
"Some services on the routes from Norwich, Ipswich, Harwich, Clacton, Braintree, Colchester, Chelmsford, Southminster and Southend to London are expected to be affected."
The company promised that ticket restrictions would be lifted if the alterations go ahead and claimed that off peak trains said off peak trains are "scheduled to run as normal".
Tfl Rail said its services were not directly affected by the fault at Liverpool Street but said: "We anticipate services being busier than normal. Please allow extra time for your journeys."
