The  V-piers are designed to support the viaduct deck over a series of lakes the Colne Valley Viaduct crosses between the end of the London tunnels and the start of the Chiltern tunnels.

Designed to bear the weight of the 80m wide arches over the lakes, the ‘v-piers’ are twice as large as simpler piers that carry the viaduct over land.

The ‘V piers’ will support a row of elegant arches whose design was inspired by the flight of a stone skimming over the surface of the water.

Cast in place using a series of giant moulds, each pier has a separate tower crane, with a temporary access bridge linking them with the main construction site. Cofferdams were used to hold back the water while the 60m deep foundations were built into the bed of the lakes.

Each pier weighs around 1,800 tonnes and took nine months to complete. To help the engineers master the complex shape of the pier, a mock-up was built off site before work began on the real piers.

The Colne Valley Viaduct – which is being built near Hillingdon – will carry high speed trains more than two miles (3.4km) across the Grand Union Canal, River Colne, local roads and a series of lakes

In total, 11 ‘v-piers’ will support the viaduct over water with a further 45 piers on land.

A 160m long bridge-building machine, known as a ‘launching girder’, will be used to lift the giant concrete deck segments that form the viaduct’s arches into position. Once each section is complete, the machine inches itself forward to build the next stage.

Originally built in 2004, the launching girder was first used during the construction of the Hong Kong East Tsing Yi Viaduct. The machine is named ‘Dominique’ in memory of Bouygues engineer Dominique Droniou who played a leading role in its design.

Deck segments will be placed alternately on each side, using a cantilever approach to balance the structure, as two half-arches are constructed simultaneously. Steel tensioning cables are then threaded through the segments to strengthen the bridge.

Align Project Director, Daniel Altier said:“I am delighted that by working as an integrated team with our supply chain partners, we have been able to erect nearly a third of the deck and complete the first V pier, just a year since Dominique starting operating.”

In the last year, it has installed over 300 out of 1,000 segments required to complete the viaduct deck, installing up to three pairs of segments each day.

To allow for the gentle curve of the viaduct, each of the one thousand segments that form the arches and deck are slightly different – and all are manufactured at a temporary factory set up close by, with direct access to the M25.

Aerial showing the extent of the 3.4km Colne Valley Viaduct once complete

The huge viaduct project is being led by HS2’s main works contractor Align JV – a team made up of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick working with key suppliers including VSL, Kilnbridge, Tarmac and KVJV.