Engineering work is taking place between Hitchin and Welwyn North all day, closing various lines throughout the day.
Before 09:00:
Buses will replace trains between Welwyn Garden City and Peterborough.
A limited train service will run between Cambridge and Finsbury Park, with journey times extended by up to an hour. A shuttle train service will run between Cambridge and Hitchin to connect with replacement buses.
One northbound train will run, the 07:44 Finsbury Park to Cambridge service.
From 09:00 until 10:00:
No trains will run from Hitchin towards Welwyn Garden City / London stations.
An amended timetable will be in place for trains running towards Cambridge / Peterborough. A shuttle train service will run between Hitchin and Peterborough / Cambridge, and also between Hitchin and Welwyn Garden City / Finsbury Park.
Replacement buses will run between Hitchin and Welwyn Garden City.
After 10:00:
All Great Northern and Thameslink services towards London stations will run to a revised timetable.