All East Coast train services between London Kings Cross and Peterborough are suspended for the rest of today due to overhead powerline damage at Huntingdon.
http://www.nationalrail.co.uk/service_disruptions/today.html has detail on all disruption but bear in mind that things can change faster than the info can be distributed. And sections which are supposed to be open, like north of Peterborough, can be disrupted if the train and crew are stuck the wrong side of the blockage.