HS2 has begun work on the UK’s longest railway bridge, with contractors sinking the first of almost 300 piles that will form the foundations for the Colne Valley Viaduct.

The viaduct, which will carry the new high-speed rail line for 3.4km on the north-west outskirts of London, will be almost a kilometre longer than the Forth Rail Bridge in Scotland.

The Grimshaw-designed viaduct includes a series of spans, some up to 80m long, carrying the railway around 10m above the surface of lakes, the River Colne and the Grand Union Canal.

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