HS2鈥檚 tunnel boring machine (TBM) Mary Ann broke through on Friday 9th May 2025, marking the end of her mission to excavate the first bore of what will soon become the longest railway tunnel in the West Midlands.
The 125-metre-long machine began constructing the 3.5-mile (5.8km) Bromford Tunnel, which starts at the Warwickshire village of Water Orton and extends to the northeast Birmingham suburb of Washwood Heath, in July 2023. The TBM was named Mary Ann, by the local community, in a nod to the Warwickshire-born writer better known by her pen name George Eliot.
The tunnel breakthrough comes as construction work on the structures being built to carry HS2 hits a peak, with around 31,000 people now employed on the programme across the 140-mile route.
Main contractor Balfour Beatty Vinci (BBV), worked around the clock for nearly two years to complete the first section of the tunnel. At peak production, the TBM advanced at around 30 metres per day.
The second bore is expected to be completed later this year by TBM Elizabeth. Following the excavation, teams will begin fitting out the tunnel with cross passages, concrete finishing works and base slabs, and emergency and maintenance walkways.
During the 22-month-long mission, the team on board the 1,600-tonne machine worked at depths of up to 40 metres. They drove Mary Ann under the Park Hall Nature Reserve, the M6 motorway, and the meandering River Tame 鈥� which they crossed four times, with a headspace as low as five metres.
The Washwood Heath site, where Mary Ann broke through, will soon become the nerve centre for HS2鈥檚 operations. HS2鈥檚 Depot and Network Integrated Control Centre will be built next to the tunnel portal. From this site, trains will be serviced and stored, and the real time operation of the railway will be controlled.
HS2 Ltd chief executive Mark Wild said: 鈥淭oday鈥檚 breakthrough is a significant milestone for the project and I鈥檓 immensely proud of the men and women who have worked day and night to bring Mary Ann and her crew home safely.
鈥淲ashwood Heath is set to become one of the most important sites on the entire HS2 network 鈥� the point at which the railway will be operated, controlled and maintained using the very latest digital technology.鈥�
Mary Ann excavated around one million tonnes of spoil during the tunnel drive. The excavated earth is being reused to support construction of the nearby Delta Junction, a network of 13 viaducts that will enable high speed trains to travel between London, the Solihull Interchange Station and Birmingham Curzon Street Station. The excavated material is transported via dedicated haul roads to minimise the number of construction vehicles on public roads.
Concrete tunnel segments were pre-cast at BBV鈥檚 yard in Avonmouth near Bristol. The TBM lined the tunnel walls with 20,797 individual segments, making 2,971 concrete rings to form the tunnel.
BBV tunnelling director Jules Arlaud said: "It鈥檚 been a challenging drive beneath critical live infrastructure and through complex ground conditions. I鈥檓 incredibly proud of our entire team, whose expertise, dedication and resilience has made this possible.
鈥淭his achievement follows years of design, planning and preparation from BBV, in close collaboration with HS2 and our partners. The team will now move onto the next phase of work inside and outside of the tunnel, while our second TBM, Elizabeth, continues to make great progress on the second drive.鈥�
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