Improvement works to stop trains for two weekends
BBCEngineering works will halt trains between London and Peterborough for the next two weekends.
Passengers have been urged to plan ahead as trains between London and Peterborough, Royston and Stevenage via Hertford North have all been stopped.
Improvements will be made to the track, drainage and overhead lines from 25 to 26 January and between 1 and 2 February.
Network Rail infrastructure director, Simon Pumphrey, said: "This work is carefully planned to maximise the time when there are track closures, allowing us to undertake several projects at once and avoiding more frequent track closures."
There will be no Thameslink or Great Northern services between London and Peterborough, Royston and Stevenage via Hertford North.
Other operators, heading further north, will run reduced services, some with rail replacement bus services.
Mr Pumphrey said: "We're sorry to passengers affected by the disruption and thank them for their patience as we make improvements that will help make the railway more reliable."
Preparatory work will also take place as part of the East Coast Digital Programme.
Customer service director at Govia Thameslink Railway, Jenny Saunders, said: "We've arranged replacement buses, shuttle trains between Royston and King's Lynn, and ticket acceptance on other routes to help you complete your journeys."
Engineering work will include renewing the line north of Stevenage and investment in bridge timbers south of Finsbury Park.
At Welwyn Garden City, upgrades will be made to the switch and crossing equipment and tunnel drainage work will be undertaken at Hadley Wood.
Improvements will be made to the overhead line kit at Biggleswade and Bounds Green and under-track cables will be installed between Biggleswade and Peterborough.
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