There are delays of up to 25 minutes on East Coast and First Capital Connect trains running through St. Neots.
Work to repair damaged cables over night is complete and all lines reopened at 6.20am this morning.
It is affecting both First Capital Connect and East Coast services between Peterborough and London King's Cross.
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