There are delays of around 30 minutes on trains from Milton Keynes to London because of overhead wire problems.
London Midland, Southern and Virgin Trains are affected.
Abellio, who run the Greater Anglia rail line, has been named Train Operator of the Year at the annual national Rail Business Awards.
Greater Anglia train operator Abellio says it's made real steps in customer service and punctuality in its first year in charge.
Greater Anglia have apologised for the delays that have disrupted services today