The huge deck segments each weighing up to 140 tonnes are being made at a purpose-built 100m long factory building that is bigger in internal volume than the Royal Albert Hall.

The construction team, which includes VSL, Danny Sullivan, Sendin and Tarmac, will cast and install a total of 1,000 concrete segments, each the size of a double-decker bus.

At the peak of construction, around 12 segments will be cast every week using a ‘match-casting’ technique.

This sees each segment poured against the previous one as a cast to ensure the whole arch fits perfectly when reassembled on site.

Every segment will be a slightly different shape depending on where it fits into the viaduct.

Vast temporary pre-cast segment factory ensures quality, safety and efficiency in production, and avoid bringing segments in by road.

HS2 Project Client, David Emms said: “We’re already making strong progress on the Colne Valley Viaduct – sinking the foundations, building the first piers, and now starting production at the new modular viaduct factory.

“Once complete, this iconic structure will carry trains at up to 200mph – improving connections across the UK, freeing up rail capacity and offering passengers low carbon travel options.

“It’s great to see how much progress has been made and I look forward to seeing work on assembling the deck structure later this year.”

Daniel Altier, Align Project Director “Seeing the first deck segments being cast in the factory marks a significant milestone for the project. The design of the viaduct is such that each segment will be unique, delivering a structure which I have no doubt will be one of the most striking elements of HS2 once complete.”

The design of the Colne Valley Viaduct was inspired by the flight of a stone skipping across the water, with a series of elegant spans, some up to 80m long, carrying the railway around 10m above the surface of the lakes, River Colne and Grand Union Canal.

Work has also begun on the 56 giant piers that will support the viaduct, working from north to south.

Weighing in at around 370 tonnes, the first 6m tall reinforced concrete pier was cast on site by a team of engineers who used a specially-designed formwork to create the shape of the structure. This was then removed after 4 days to reveal the final product.

Each pier is designed to support the full weight of the deck above and rests on a set of concrete piles going up to 55m into the ground. This foundation work began earlier this year and will require the construction of 292 piles and 56 pile caps across the whole length of the viaduct.

Once complete, the team will then use a specialised ‘launching girder’ resting on top of the piers to lift the deck segments into position.