The 17-strong crew working the enormous Florence TBM achieved an average speed of 16m a day on the 10-mile journey under the Chilterns.

The 2,000-tonne TBM is one of 10 machines excavating the 32 miles of tunnel on the HS2 project from London Euston to Birmingham.

Main works contractor Align’s other sister TBM, Cecilia is driving the second of the bores on the route will breakthrough in the coming weeks.

International effort: Breakthrough at the North Portal, near South Heath in Buckinghamshire

HS2 Executive Chairman, Sir Jon Thompson, said: “Today is an incredible day of HS2 and I’d like to thank the hundreds of people who’ve worked so hard over many years to make it happen.

“We’ve still got a lot of work to do, but historic moments like today really underline the huge amount of progress that’s been made and the fantastic engineering skills we have on the project.”

Each TBM crew worked in shifts to keep the machines running 24/7. They are supported by over 100 people on the surface, managing the logistics and maintaining the smooth progress of the tunnelling operation.

In total, more than 450 people have worked on the tunnels and in support teams on the surface over the last 2 years and nine months.

This includes a dedicated team which produced 112,000 precision-engineered, fibre-reinforced concrete tunnel wall segments at a purpose build temporary factory at the South Portal who completed their work just before Christmas – and a team processing the spoil from the tunnels.

The 3 million cubic metres of chalk and other material removed during the tunnelling is being used to create an ambitious grassland restoration project at the south portal, which will include 127 hectares of new landscaping, wildlife habitat and biodiverse chalk grassland.

Align JV’s partners – Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick – are also delivering the record-breaking Colne Valley Viaduct which will be the longest railway bridge in the UK, with construction of the deck now over two-thirds complete.