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.
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.
Delays remain on the trains this morning due to overhead line problems in Hertfordshire.
All lines are re-opened, but there are still 20-minute delays on First Capital Connect and East Coast trains heading into London King's Cross, due to speed restrictions.
Signalling problems between Hitchin and Stevenage are causing delays of about 30 minutes on East Coast trains between Peterborough and Kings Cross
That is also affecting First Capital Connect services between Cambridge and Kings Cross, and Peterborough and Kings Cross with delays of 30 minutes.
There are delays of up to three hours on some East Coast journeys to and from London King's Cross because of a broken down train. The train has now been moved and delays are beginning to ease.
Disruption on East Coast between Peterborough and Doncaster due to signalling problem.
Trains are not able to use some of the lines north of Peterborough whilst Network Rail engineers try and fix the problem. Several trains are delayed. May also affect some First Hull Trains and Grand Central.
Delays of up to 40 minutes on East Coast and First Capital Connect trains due to signalling problems between Peterborough and London King's Cross.