A replacement bus service is running on the London Midland service between St Albans Abbey and Watford Junction due to broken down train.
There is no current estimate for when a normal service will resume.
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