Dartford Cable Tunnel
The Dartford Cable Tunnel is a 2.4 km tunnel upstream of the Dartford Crossing. With a diameter of ~, it is designed to carry and allow for maintenance of 400 kV National Grid electrical cable beneath the Thames. It is accessible by foot as a crossing of the Thames, but by authorised personnel only. It was built in 2003–04 at a cost of £11,000,000.
