And the closure means all services will start and finish at Milton Keynes Central instead.
Upgrades will also take place to switches and crossings – the equipment which lets trains move between lines.
The work involved mean no trains will serve London Euston between Good Friday and Easter Monday, April 15 to April 18.
It will see 1km of new track installed, 5,000 tonnes of new railway foundation stone (ballast) laid and 4,400 of spoil removed. Some 7,000 worker hours will be carried out over 14 shifts, and there will be 10 engineering trains, two rail mounted cranes and eight rail mounted excavators to move stone and spoil.
Once complete the railway renewals will increase the number of trains which can pass through the key junction, meaning fewer delays and faster journeys for passengers and freight in future.
As well as the track improvements, engineers are making the most of the full railway closure to carry out a wide range of other work, including drainage, fencing, station maintenance and bridge surveys.
Passengers needing to travel on the days in between could have longer journeys, fewer available seats, and may need to use rail replacement buses.
James Dean, Network Rai’s West Coast South route director, said: “There is never an ideal time to shut the railway and we have to carefully balance the best time to do this essential work with the needs of our passengers. Long bank holiday weekends continue to give our engineers the time they need to close the railway for complex jobs like track replacements and bridge overhauls while disrupting the fewest passengers.
“Our advice this Easter is to travel either side of the bank holiday weekend and to plan ahead by checking National Rail Enquiries to see how your journey could be impacted by our essential upgrades to improve the railway for the future.”
Visit National Rail Enquiries or your local train company website for information about specific journeys.