HS2 has started excavation of the final tunnel bore on the 140-mile railway between central London and the West Midlands – marking a significant milestone for the project.
Today (16 March), the last of 11 tunnelling machines built for the 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 Madeleine, 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, putting the programme’s construction in the right sequence and bringing certainty to the railway’s final costs and opening dates. Led by HS2’s Chief Executive Mark Wild, the reset will put HS2 back on track and unlock the project’s transformational benefits – vital new rail capacity and economic growth.
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.”
The TBM was named Karen in keeping with the tradition of naming tunnelling machines after prominent women. In a nod to the remarkable woman behind the name, two current female train drivers, Hayley Richardson and Vicky Knight, from Avanti West Coast visited the site to mark the start of tunnelling and were given the opportunity to operate the machine alongside the engineering team.
Avanti West Coast is the current operator of intercity rail services on the West Coast Main Line, connecting London with Birmingham, as well as Manchester, Liverpool, Glasgow and North Wales.
Hayley said:
“It is a fantastic privilege to be part of this latest milestone for HS2 – it’s not every day you get to swap a train cab for the controls of a tunnelling machine.
“For it to be named Karen is a wonderful tribute to a pioneering woman who helped pave the way for female drivers today.”
Vicky said:
“Karen Harrison’s story is one to admire, and it is great she is getting the recognition she deserves for the influential role she played in shaping our industry.
“I’m honoured to take part in this event to celebrate her legacy, as well as mark another key moment in building the railway of the future.”
The TBM is the final machine to be launched on HS2 to complete the bored tunnels on the HS2 route between the West Midlands and London. Four other tunnels have now been completely bored – the Northolt, Chiltern, Long Itchington Wood and Bromford tunnels.
Euston is the second bored tunnel underneath the capital – after the Northolt Tunnel – and is being constructed by HS2’s London tunnels contractor, Skanska Costain STRABAG joint venture.
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.
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.”
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.
The journey to central London will see the TBM pass under the final resting place of Isambard Kingdom Brunel in Kensal Green cemetery. Brunel is widely celebrated as one of the world’s most ingenious figures in engineering history, and who also set standards for building a modern railway.
