The operator has allowed passengers to defer their tickets today due to the disruption caused after thieves stole signalling cables.
It means tickets dated for Monday (June 27) will be valid on both Tuesday and Wednesday.
A Network Rail spokesperson said: “Due to the theft of signalling cable, there are severely limited train services on the East Coast Main Line this morning (Monday 27 June) between London King’s Cross and Peterborough.
“There will only be up to two trains an hour each way on either LNER or GTR services and this disruption is expected to last until at least midday.
“Our engineers are currently onsite making the necessary repairs and we’re sorry for this disruption and thank passengers for their patience and understanding during this time.
“Passengers are advised to check before travelling and plan ahead.”