HS2 has launched the final tunnel boring machine (TBM) required to complete the railway’s extensive tunnelling programme between London and the West Midlands, marking a major milestone for the project.
The machine, named Karen, began its journey on 16 March from Old Oak Common towards Euston, where it will excavate the second bore of the 4.5-mile Euston Tunnel.
Karen is the last of 11 TBMs used across the HS2 route and follows the launch of its sister machine, Madeleine, earlier this year. Together, the two machines will create twin tunnels bringing high-speed services directly into central London.
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.”
Final stage of a major tunnelling programme
The Euston Tunnel is one of the final major tunnelling elements on the 140-mile HS2 route, with four other tunnels – Northolt, Chiltern, Long Itchington Wood and Bromford – already complete.
Once finished, the tunnel will provide a direct high-speed link into Euston station, improving capacity on the rail network and enabling faster, more reliable journeys.
Alan Morris, HS2 Ltd’s Line of Route Delivery Director, 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 tunnelling work is being delivered by HS2’s London tunnels contractor, the Skanska Costain STRABAG joint venture (SCS JV).
A 24/7 underground operation
The 198-metre-long TBM operates as a continuous underground factory, excavating earth while installing precast concrete segments to form the tunnel lining.
Across both tunnel bores, the machines will install 48,294 concrete segments and remove around 1.5 million tonnes of excavated material.
Jonathan Morris, Managing Director of the SCS 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.”
Excavated material is transported via conveyor to the Willesden Euro Terminal logistics hub, before being moved by rail for reuse at sites across the UK – removing more than 135,000 lorry movements from the road network.
Recognising rail pioneers
In keeping with tunnelling tradition, the machine has been named after a notable woman – Karen Harrison, one of the UK’s first female train drivers, who began her career at Old Oak Common.
To mark the launch, two Avanti West Coast drivers, Hayley Richardson and Vicky Knight, were invited to operate the TBM alongside engineers.
Hayley Richardson 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 Knight added: “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.”
Progress amid wider project reset
The milestone comes as HS2 continues a wider programme reset, led by Chief Executive Mark Wild, aimed at improving delivery certainty around costs, sequencing and timelines.
Despite ongoing challenges, the completion of the tunnelling programme is a critical step towards delivering HS2’s long-term objectives of increasing rail capacity, supporting economic growth and improving connectivity between London and the Midlands.
