The project’s first two Tunnel Boring Machines (TBMs) – named Florence and Cecilia – are due to launch in early summer.

Each of the 170m long, 2,000 tonne machines will spend more than three years underground, digging and slotting the wall segments into place to create the 10 mile long tunnels.

The fibre-reinforced concrete segments are being produced at a temporary pre-cast factory next to the TBM launch pads at what will be the south portal of the tunnels.

This will avoid putting extra HGVs on local roads and ensure a steady supply of segments for the TBMs.

Once construction is complete, the pre-cast factory and the rest of the south portal site, will be cleared, with the chalk excavated from the tunnels used to landscape the site and create grassland and other wildlife habitats.

Construction of the Chiltern tunnel, and nearby Colne Valley Viaduct, is being led by HS2’s main works contractor, Align JV of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick.

Didier Jacques, Align’s Underground Construction Director said: “We are using Steel Fibre Reinforced Concrete (SFRC) in the segments due to the improved ductility and durability it offers. The SFRC segments are also easier to fabricate.

“Once in the moulds we are using robots to polish the concrete, a task that was previously manual, to improve the quality and consistency of the final product.

“With 7 segments in each ring, we will be producing a total of 160 rings ahead of launch of the first TBM later this year.”