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Commuters in the East will face major disruption due to the closure of London King's Cross tomorrow, Saturday and Sunday.
Thameslink and Great Northern passengers have been urged not to travel on the railway this weekend.
Watch Network Rail's timelapse video of the work at London King's Cross
No trains will run to or from London King's Cross as major upgrades are made to the signalling system.
Network Rail, Great Northern and Thameslink advise passengers to check their journeys before travelling.
On Saturday and Sunday there will be extensive closures across the East Coast route including no trains via Finsbury Park to or from King's Cross, St Pancras or Moorgate.
FRIDAY 23RD APRIL - The following changes will be put in place:
Great Northern and Thameslink services that usually run to/from London Kings Cross will start/end at Finsbury Park for connections with London Underground services to King's Cross.
Thameslink services to/from London St Pancras International and Great Northern services to/from Moorgate will continue to run. For the easiest journey, passengers travelling to or from central London are strongly encouraged to use these services instead to avoid the long walk between the National Rail and Underground platforms at Finsbury Park.
LNER trains to/from the North of England and Scotland will start/end at either Peterborough or Stevenage, where passengers can change onto Thameslink train services to/from St Pancras International.
Grand Central will run a reduced service between Sunderland/Bradford and Finsbury Park.
Hull Trains will not run.
SATURDAY 24TH APRIL and SUNDAY 25TH APRIL - The following changes will be put in place:
A very limited Thameslink and Great Northern service will run over the weekend.
No trains will run to/from London King's Cross, Moorgate or to/from London St Pancras International via Finsbury Park.
Trains will run between Peterborough and St Neots, between King's Lynn, Cambridge and Letchworth Garden City, and between Welwyn Garden City and Potters Bar only. A number of rail replacement bus routes will connect with alternative rail services or London Underground lines for onward travel into London.
LNER trains to/from the North of England and Scotland will start/end at either Peterborough or St Neots. A replacement coach service will run between St Neots and Bedford, where passengers can change onto Thameslink train services to/from St Pancras International.
Grand Central and Hull Trains services will not run to or from London.
People should continue following the latest Government guidance and minimise travel where possible.
Passengers who need to travel are strongly advised to check their journey via National Rail Enquiries, at EastCoastUpgrade.co.uk or with their train operator. They should also allow extra time as journeys will take longer than usual.
A full service will resume on Monday.