Dartford Cable Tunnel
The Dartford Cable Tunnel is an underground tunnel under the River Thames in the United Kingdom, just upstream from the Dartford Crossing. It is 2.4 kilometers long and about 3 meters in diameter. The tunnel carries a 400 kV AC electrical transmission cable owned by National Grid.
The tunnel can be walked through as a crossing of the Thames, but entry is restricted to authorized personnel only. It was built in 2003–2004 at a cost of about £11 million (around £22 million in 2023 prices).
This tunnel helps keep the power supply reliable by moving high-voltage electricity safely beneath the river.
This page was last edited on 3 February 2026, at 00:01 (CET).