National Grid Completes Thames Tunnel Drive 49 Days Early
Tilbury – October 11, 2026 -- National Grid's tunnel boring machine (TBM) Caroline completed a 2.2km drive beneath the River Thames 49 days ahead of the original programme, ending the tunnelling phase of the Grain to Tilbury project, part of The Great Grid Upgrade.
The breakthrough came on Sunday 27 September. Caroline excavated a new high-voltage electricity cable tunnel between Tilbury in Essex and Gravesend in Kent.
Caroline installs more than 10,000 segments across nearly 1,700 rings
The tunnel lining consists of more than 10,000 concrete segments assembled into nearly 1,700 tunnel rings. In her most productive month, Caroline advanced 926 metres and installed 712 lining rings. Peak weekly progress reached 229 metres, and the best single day delivered 41 metres of excavation and 31 installed rings in 24 hours.