HS2 has announced a "significant milestone" at Long Itchington Wood Tunnel in Warwickshire – the first deep tunnel on the high-speed route to complete its civil engineering phase.

The development at the one-mile-long twin-bore tunnel – which will carry the railway into the West Midlands – sees "vital elements", including three cross passages, concrete finishing works and base slabs, and emergency and maintenance walkways complete.

It comes before the internal fitting out of the tunnel with the "complex systems" needed to operate the high-speed line including the power, track and signalling.

The tunnel is the first of five twin-bore tunnels on the HS2 project to reach this vital stage.

In all, 27.4 miles of the route between London and the West Midlands are in deep, twin-bore tunnels.

Work to create the Long Itchington Wood Tunnel began in June 2020.

The 125-metre-long tunnel boring machine used to excavate the tunnel was named 'Dorothy' – after Dorothy Hodgkin who was the first British woman to win the Nobel Prize in Chemistry.

The machine was launched in December 2021 and finished excavating both bores of the tunnel by March 2023.

The complex process to fully excavate two tunnel drives and the entrance sections produced around 750,000 tonnes of material, which has since been reused to build embankments along the route of the railway.

The tunnel in Long Itchington is a mile long (image via HS2)

Since the breakthrough almost two years' ago, work has been ongoing to fit out the tunnels with its vital structural components.

Doug Barnett, senior project manager for HS2 Ltd, said: "It's a small part of HS2 but it's been four and a half years of my life in which I've seen this construction go from its very embers to nearing completion – a really proud moment for me personally.

"Long Itchington Wood Tunnel is a tremendous feat of engineering and would not have been possible without a huge amount of continuous work put in over the past five years – I'd like to thank everyone involved working both onsite and behind the scenes for their support."