A major railway upgrade will affect Grantham services this weekend.

Network Rail will carry out vital work to connect a new tunnel north of Peterborough to the existing railway, ready to further improve journeys for passengers on the East Coast Main Line.

The project at Werrington will allow slower moving freight trains to dive underneath the famous passenger route.

It is part of the £1.2billion East Coast Upgrade, which has also seen major work completed to transform the track layout and reopen a tunnel at King's Cross, making it easier for more trains to enter and exit the station.

Back in January, engineers pushed the world's longest single underground jacked structure – an 11,000-tonne curved concrete box - into place at Werrington, in a UK first for engineering.

Since then, vital work has taken place to install around 4km of track inside the new tunnel, as well as signalling equipment, without disrupting train services.

On Saturday 17 and Sunday 18 July, engineers will carry out an essential part of the project - to connect the new track to the existing Stamford lines.

During the weekend, services will continue running for passengers on the East Coast Main Line, however a section of the line between Peterborough and Stamford will be closed to allow teams to connect the tracks safely. The following changes will be in place to keep passengers moving:

Buses will replace CrossCountry trains between Peterborough and Leicester on Saturday 17 and Sunday 18 July.

On Saturday 17 July, the 05:00 and 06:08 East Midlands Railway services between Nottingham and Norwich will be diverted via Grantham. These trains will not call at East Midlands Parkway, Loughborough, Melton Mowbray, Oakham or Stamford and bus replacement services will run.

Ed Akers, Principal Programme Sponsor for Network Rail's East Coast Upgrade, said: "We used challenging industry leading techniques to push the tunnel into place and our teams have continued to work around the clock to install the new track without impacting on services.

"This work to connect the tunnel to the existing lines is only possible when there are no trains running on this section of the route. We've carefully planned the work and have bus replacements in place to keep passengers moving. We want to thank people for their patience whilst this vital stage of the project is carried out."

Work on the dive-under is expected to be completed over the summer, ready for train services to use it later this year.