The milestone was reached on the Chipping Warden Green Tunnel in Northamptonshire where faults were found in 2022 in precast concrete segments.

With the pre-cast wall installation finished, the construction team are now focused on completing the waterproofing and internal floor slab and all other internal works, including the emergency walkways that will run alongside the track.

To speed up construction, the tunnel was built in two parts, which joined together last week with the final segments lifted into position near the A361.

Chipping Warden is one of three tunnels being built by HS2’s main works contractor in this area, EKFB – a team made up of Eiffage, Kier, Ferrovial Construction and Bam Nuttall.

Lessons learnt are also being applied to the tunnels at Wendover and Greatworth, which both use a similar pre-cast approach.

EKFB’s Senior Project Manager, Chris Barrett said: “Watching the final tunnel segment being lifted into place is the outcome of 18 months of rewriting the playbook, learning, innovating and putting the right solutions forward when challenged, all of which have boosted on site productively.

“This success has allowed EKFB to safely work at twice the speed compared with the start of construction works in 2023. Now our focus shifts to completing waterproofing and internal works as well as backfilling earth around the tunnel and by the end of winter, it’ll be buried and largely out of sight.”