A curved concrete box weighing more than the Eiffel Tower has been pushed under a railway line to form a new tunnel, in a "UK first" for engineering.
The 11,000-tonne, 155m (510ft) structure was moved into place under the East Coast Main Line at Werrington, Peterborough, at 150cm (60in) per hour over nine days.
The tunnel, opening at the end of 2021, will separate freight and passenger trains on the London to Edinburgh route. Network Rail said it would lead to faster and more reliable services.
The project is part of £1.2bn being spent to upgrade the line. A spokeswoman for Network Rail said it was the "first time this technique has been done using a curved concrete box structure in the UK".