Between King's Lynn, Cambridge and London King's Cross, further changes are being introduces from Monday 26th September.
The changes on the route will allow work to repair track defects as a result of the recent heatwave to commence.
The spike in temperatures and lack of rain resulted in the peaty ground under the tracks to dry out and shrink.
To compensate for this, a temporary speed restriction was put in place to allow for services to run safely.
However, to prevent further damage to the tracks and allow normal speeds to resume, the repair work needs to be completed as soon as possible.
Engineers have been realigning the track over the past four weeks which has allowed for some of the restrictions to be removed but not enough to allow the full timetable to run reliably.
Network Rail and Thameslink have made the decision to close the line early at 20:45, Monday to Friday, until Tuesday 4th October to minimise the disruption to passengers and get the work completed quicker.
This will hopefully remove most of the speed restrictions and restore the timetable from Wednesday 5th October.
The last trains will run from King's Lynn and Ely around 20:00, with further updates to be provided in the next week.
More information and updates on final checks can be found at www.greatnorthernrail.com or www.nationalrail.co.uk
Ellie Burrows, Network Rail's route director for Anglia, said: “We recognise the impact this is having on passengers, so this remedial work is being carried out as a priority. The early closure of the line will help to speed up this work. I am very sorry for the delays and thank passengers for their patience while we carry out these repairs.”
Jenny Saunders, Customer Services Director for Great Northern and Thameslink, said: “We're sorry for the continued changes we're having to make to our rail service between Kings Lynn, Cambridge and London but it is absolutely essential to ensure the continued safe running of our trains and to give our customers a dependable service.
“We'll continue not running some of our trains between London and Cambridge or Ely in the meantime, which will make other services busier, and passengers for stations along the route to King's Lynn will have to continue changing at Cambridge until the direct service can be restored.”
