The tunnel is comprised of ‘rings', each of which is formed of seven concrete segments. The first tunnel boring machine (TBM) to launch has now completed more than 1,000 rings.
Millicent, the TBM responsible the central delivery team's westbound drive, was working deep underground somewhere beneath Albert Bridge and Battersea Bridge, with around 3km to go until Carnwath Road in Fulham.
The previous record for ‘longest tunnel beneath the Thames' was held by the 1.3km HS1 tunnel, which crosses between Kent and Essex at Ebbsfleet.
All spoil from the tunnelling operation at Kirtling Street, where Millicent launched, is being removed from the site by barge.
Tideway's commitment to using the river to transport as much material as possible is keeping thousands of lorries off London's roads.
More than one million tonnes have now been transported by river across the project.