Dartford Cable Tunnel

The Dartford Cable Tunnel is a 2.4 km utility tunnel beneath the Thames, upstream of the Dartford Crossing. With a diameter of ~3 m, it carries a 400 kV National Grid electrical transmission cable. 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 million (equivalent to £ million in ).