Today (16 March), the last of 11 tunnelling machines built for the HS2 London Tunnels project started its drive from Old Oak Common station in west London towards Euston – the railway’s terminus. The tunnel boring machine (TBM) is named Karen after Karen Harrison, one of the first female train drivers in the UK, who drove out of Old Oak Common depot.
To mark the milestone, two female train drivers from Avanti West Coast were invited onto the machine to drive it alongside the engineers working on the project.
The launch comes hot on the heels of TBM Madeline, the first of two machines being used to excavate the twin-bore tunnel, which was launched in January. TBM Karen will complete the second bore of the 4.5-mile Euston Tunnel which will bring Britain’s fleet of high-speed trains directly in and out of the heart of the capital – improving capacity of the rail network and providing passengers with more reliable and faster journeys.
The government’s commitment to a new HS2 station at Euston is vital for the wider regeneration of the Euston area, acting as a catalyst for investment and creating new homes and employment opportunities.
The launch comes as HS2 continues to undergo a comprehensive reset led by HS2’s Chief Executive Mark Wild, putting the programme’s construction in the right sequence and bringing certainty to the railway’s final costs and opening dates
Rail Minister, Lord Hendy, said: “Today’s launch brings HS2’s journey to Euston another step closer to reality, as this Government presses on to deliver this project and with the transformational Euston station redevelopment.
“We’re putting HS2 back on track, and taking the railway into central London is crucial to unlocking its full potential to deliver more jobs, more homes and a long-term boost to the whole British economy.”
Alan Morris, Line of Route Delivery Director, HS2 Ltd, said: “The launch of the final HS2 TBM towards Euston is significant milestone in our extensive tunnelling programme. TBM Karen will complete the second bore of the Euston Tunnel, bringing high speed train services directly in and out of the centre of the capital, enabling future economic growth and regeneration.
“While we have been working hard to reset the project, our expert teams have been focused on safely driving up productivity - and today’s final TBM launch is real evidence of that paying off.”
Jonathan Morris, Managing Director of Skanska Costain STRABAG joint venture said: “We are proud to launch HS2’s final tunnel boring machine, a major milestone for both SCS JV and the wider project as we excavate the twin-bore tunnel towards Euston. During this work the TBMs will remove over 1.5 million tonnes of excavated material and construct the final section of the tunnels using more than 8,000 pre-cast rings.
“Our teams have already delivered 8.4 miles of tunnels under London and will now continue working around the clock to complete these final drives. Achieving this safely and productively is our top priority, with our TBMs progressing at an average rate of around 16 metres per day while maintaining the highest levels of safety performance.”
Euston is the second bored tunnel underneath the capital, after the Northolt Tunnel.
The giant tunnelling machine was manufactured by the world’s leading TBM supplier, Herrenknecht AG, in Germany, before being shipped to the UK and reassembled in the underground station box at Old Oak Common.
The 198-metre long machine operates as a 24/7 underground factory, excavating the earth and installing concrete segments into rings to create the tunnel. Overall, on both bores of the tunnel, 48,294 concrete segments will be installed, and 1.5 million tonnes of spoil will be excavated. Each 6-tonne concrete segment has been manufactured by STRABAG in a newly-established facility in Hartlepool, UK, before being transported down to the capital by rail.
The tunnelling operation for the Euston Tunnel is being facilitated by a separate temporary logistics tunnel which was completed in January 2024. The 853-metre Atlas Road Logistics Tunnel will allow the tunnelling team to access both machines, deliver construction materials and remove the excavated spoil. All the excavated material from the tunnel will be taken via conveyor to the London Logistics Hub at the Willesden Euro Terminal Depot. From there it is taken by rail for reuse in projects in Kent, Cambridgeshire and Warwickshire, taking more than 135,000 trucks off the road.
The TBM has been launched underground from the Old Oak Common station box, 23m below ground. At its deepest, the Euston Tunnel will be 66 metres below ground. Once the TBM finishes its journey, it will be parked and key elements of the machine will be pulled back through the tunnel. The cutterhead, spanning 8.53-metres will be excavated from the Euston Cavern and removed. The outer part of the front of the machine, known as the shield or ‘can’, will remain underground and will be grouted in behind the concrete tunnel lining.