The names – Florence and Cecilia – were inspired by scientific and medical pioneers.

The first two TBMs will be operated by HS2’s main works contractor, Align JV – a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick.

The 2,000 tonne machines – which have been built by German tunnelling specialists Herrenknecht – will be shipped in pieces to the UK and arrive at Align’s main site to the west of London just inside the M25 later this year.

‘Florence’ is set to be launched early next year to begin digging the 10-mile-long Chiltern tunnel. ‘Cecilia’ will launch around a month afterwards and dig the other half of the ‘twin bore’ tunnel.

Both 170m long machines are specifically designed for the mix of chalk and flint they will encounter under the Chilterns.

Operating a ‘continuous boring’ technique, they are expected to take around three years to excavate the 9.1m metre diameter tunnels which will be lined with concrete as they go.

The TBMs will mix the spoil with water to form a slurry which will be pumped back to the main site where it will be treated before being used for landscaping on-site, removing the need for additional HGVs on local roads.

Daniel Altier, Align Project Director said: “Florence and Cecilia incorporate the latest technology which will be essential to ensure an efficient and safe excavation of the twin-bore tunnel.

“This will be the first time that some of the innovations we are introducing will have been used on any TBM worldwide.”

HS2 Ltd Chief Executive Mark Thurston said: “The launch of our first tunnelling machines will be a defining moment in the history of HS2 – and our work to deliver a low carbon, high speed railway that will change the way we travel in the UK.”