Drone footage shows the £500m water pipe that is longer than the M1
Aerial pictures showed a 205-mile (330km) pipe being laid to move water from the north of a region to the south.
The £500m pipeline - longer than the M1 motorway and running from Humberside to south Essex - is part of Anglian Water's plans to cope with population growth and climate change.
Head of media Regan Harris said it was "fundamental to keeping taps running" in the East of England.
The firm's investors are paying up front for the infrastructure and the cost will be recouped from bill payers over its lifetime.
