Mainline rail services between Norfolk, Suffolk, Essex and London have been severely disrupted after a man died on the line.
One Railway said many services between Norwich and London Liverpool Street were severely delayed or cancelled.
British Transport Police were called to an incident at Romford station in Essex at 1635 GMT.
British Transport Police said, after an interview with the driver, they are not treating the death as suspicious.
The man, who was thought to be in his 50s, was struck by the 1617 GMT London to Witham train.
A spokesman for the British Transport Police said they have a possible identity but will not release any more details until formalities are completed.
He said that overhead power lines were switched back on at 1717 GMT and this allowed services to run on two of the four rail tracks through Romford.
One Railway also reported signalling problems caused the 1640 GMT service between Norwich and Great Yarmouth via Acle to run non-stop to make up time following a delay.