HS2 is celebrating as its giant tunnelling machine, Mary Ann, broke through and completed excavating the first bore of a railway tunnel that will be the longest in the West Midlands.

Mary Ann is 125 metres long, weighs 1,600 tonnes, and began boring Bromford Tunnel in July 2023. It reached the halfway point in September last year.

The tunnel is 3.5 miles (5.8km) long, starts at Water Orton in Warwickshire and extends to Washwood Heath, a northeast Birmingham suburb.

The local community named the tunnel boring machine (TBM) Mary Ann after the writer who is better known by her pen name, George Eliot, who was born in Warwickshire.

450 engineers have worked on the tunnelling for just under two years, and have now completed the first section of the tunnel. HS2 expects to complete the second bore later this year.

Once boring is completed, workers will fit out the tunnels with cross passages, concrete finishing works, and base slabs. They also create emergency and maintenance walkways.

Mary Ann’s tunnelling work reached depths of forty metres, taking it under the Park Hall Nature Reserve, the M6 motorway, and the River Tame.

The tunnel broke through at Washwood Heath, which will become HS2’s operational centre. HS2 will build a Depot and Network Integrated Control Centre next to the tunnel portal, from which it will service and store trains, and control the operation of the railway.

Mary Ann dug out around one million tonnes of spoil during the tunnel drive, which HS2 will use in the construction of the nearby Delta Junction.

At its fastest, the TBM advanced at around thirty metres per day. The crew ensured that the cutterhead sliced through the earth, while reinforcing the excavated tunnel with 20,797 concrete segments, each of which weighs up to seven tonnes. These segments made 2,971 concrete rings to form the tunnel.

The workforce included eleven local apprentices, and HS2 hopes that this will help to address the recognised shortage of skilled tunnelling workers in the UK.

“Today’s 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.”

Mark Wild, HS2 Ltd’s Chief Executive