Dartford Cable Tunnel

The 337th longest tunnel in the world

2.4 km · Length

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 (10 ft), 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 £20 million in 2025). The tunnel plays a crucial role in maintaining electrical supply infrastructure beneath the Thames, ensuring reliable power transmission.

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Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).

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