"Urgent repairs" are set to cause disruption on the train line between Alexandra Palace and Stevenage, following a landslip.
The line towards Stevenage via Hertford North will be blocked later tonight (Thursday, February 15) into tomorrow (Friday, February 16) - along with the evening of February 16 into the morning of February 17, while the repairs are carried out.
The line will be closed between 12.30am and 5am on both nights.
A spokesperson for Great Northern said: "Our control teams are working to ensure all affected trains are identified.
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"We update journey planners as soon as possible to reflect any changes.
"Please check your journey before you travel using online journey planners at www.nationalrail.co.uk.
"For more information, please see our service updates page: www.greatnorthernrail.com/travel-information/plan-your-journey/service-updates"
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