HS2 Ltd has launched the final tunnel boring machine (TBM) on the high-speed rail line between London and the West Midlands, marking a major milestone in the project’s construction.
The 1,624-tonne machine, named Karen after pioneering British train driver Karen Harrison, has begun excavating the second bore of the 4.5-mile Euston Tunnel. Launched from Old Oak Common in west London, it will complete the twin-bore connection into central London.
The launch follows the deployment of a second TBM, Madeleine, earlier this year, with both machines working to deliver the tunnel that will connect HS2 services directly to Euston station. Once completed, the link is expected to improve rail capacity and journey times while supporting wider economic growth.
The TBM, built by Herrenknecht AG, operates as a continuous underground factory, excavating soil and installing precast concrete segments to form the tunnel lining. Over the course of the project, approximately 1.5 million tonnes of material will be removed and more than 48,000 segments installed.
Construction of the tunnel is being delivered by the Skanska Costain STRABAG joint venture, which has already completed several major tunnel sections along the route. The Euston Tunnel is the second major bored tunnel beneath the capital.
The project is seen as critical to the regeneration of the Euston area, with the potential to contribute up to £41 billion to the UK economy through new homes, jobs and improved connectivity.
The launch of TBM Karen also highlighted the role of women in the rail industry, with two drivers from Avanti West Coast invited to operate the machine during the ceremony, celebrating the legacy of one of the UK’s first female train drivers.
