There are severe delays on some trains due to overhead power line problems at St Neots.
Bus replacement services are running on East Coast trains between Peterborough and King's Cross.
There are also bus replacements on First Capital Connect between Biggleswade and Peterborough.
There are also 30-minute delays on Grand Central trains.
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