Rail passengers are being advised to double-check travel arrangements ahead of scheduled engineering works on Saturday, February 29, and Sunday, March 1.
No Thameslink or Great Northern services will be running from Biggleswade and Letchworth Garden City to King's Cross, St Pancras International or Moorgate stations - as improvement works to the East Coast Main Line continue.
Network Rail will be testing signalling equipment at Stevenage station as part of plans to build a new platform, while work will also take place to install new overhead line equipment.
Great Northern and Thameslink services will still run between Peterborough and Biggleswade, and between King's Lynn and Letchworth Garden City - but there will be no further services into London. LNER trains will only run as far south as St Neots.
Train operators on the East Coast Main Line and Network Rail announced the planned works in October, which form part of a £1.2 billion engineering investment known as the East Coast Upgrade.
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