HS2’s tunnelling machine Mary Ann broke through the first Birmingham tunnel on 9th May 2025, Bromford Tunnel, 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 5.8 km Bromford Tunnel in July 2023. The tunnel starts at the Warwickshire village of Water Orton and extends to the northeast Birmingham suburb of Washwood Heath. Two TBMs are being used to excavate the tunnel – TBM Mary Ann, launched in August 2023, is digging the first bore, while TBM Elizabeth, launched in March 2024.
Mary Ann excavated around 1 million tonnes of spoil during the tunnel drive and the excavated earth is being reused to support construction of the nearby Delta Junction, a complex network of 13 viaducts that will enable high speed trains to travel between London, Interchange Station in Solihull and Birmingham Curzon Street Station.
The precision-designed segments were manufactured at Balfour Beatty Vinci’s pre-cast factory at Avonmouth near Bristol. The TBM lined the tunnel walls with 20,797 individual segments, making 2,971 concrete rings to form the tunnel.
The tunnel breakthrough – HS2’s first in Birmingham – is a significant milestone for the project, which will almost halve journey times between Britain’s two largest cities, whilst freeing up valuable track space on the heavily congested West Coast Main Line for more local, regional and freight services.
The ground-breaking achievement comes as construction work on the giant structures being built to carry HS2 hits a peak, with around 31,000 people now employed on the programme across the 225 km route. Despite recent progress, HS2 is currently undergoing a fundamental reset to make sure the railway can be delivered efficiently and for the lowest feasible cost.
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-work, the team on board the 1,600-tonne machine worked at depths of up to 40 metres. They skilfully navigated Mary Ann under the Park Hall Nature Reserve, the M6 motorway, and the meandering River Tame – 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’s operations. Next to the tunnel portal, HS2’s Depot and Network Integrated Control Centre will be built. From this site, trains will be serviced and stored, and the real time operation of the railway will be controlled.
The “breakthrough is a significant milestone for the project and I’m immensely proud of the men and women who have worked day and night to bring Mary Ann and her crew home safely. Washwood Heath is set to become one of the most important sites on the entire HS2 network – the point at which the railway will be operated, controlled and maintained using the very latest digital technology,” Mark Wild, HS2 Ltd’s Chief Executive said.
Washwood Heath is one of three key HS2 sites in the West Midlands, alongside the two new stations that will be built in Birmingham and Solihull.
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