HS2 Ltd has unveiled its first two tunnelling machines, which have been built at a factory in Germany, before they dig through the Chilterns.

The giant contraptions will excavate a 10-mile long tunnel as deep as 80 metres below ground in the Chilterns as part of phase one of the controversial high-speed railway between London and Birmingham.

They have been named Cecilia and Florence following a public vote from a shortlist of suggestions made by local schoolchildren - a move that prompted outrage from residents against the development of the railway, who branded the competition "absurd" and an "insult".

Cecilia is named after Buckinghamshire-born astronomer Cecilia Payne-Gaposchkin while Florence comes from Florence Nightingale, the founder of modern nursing who spent many years in the county.

The other shortlisted name was Marie from Marie Curie, the first woman to win a Nobel Prize.

The 2,000-tonne machines have been built by specialist firm Herrenknecht in the small town of Schwanau, south-west Germany.

HS2 minister Andrew Stephenson said: "These impressive tunnel boring machines will be instrumental in delivering the first stage of this transformative rail line between London and the West Midlands, and it is fitting that they bear the names Florence and Cecilia, two iconic women from this area whose achievements remain famous today.

"HS2 will provide better, more reliable connections that truly level up our country, boosting economic growth and sharing opportunities. I want to thank all the students who played a role in this milestone moment and who will benefit from this high-speed railway for years to come."

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.

"I'd like to thank all the schools that took part in the first stage of the competition, the pupils who suggested the three shortlisted names and all those who voted online.

"It's great to see local communities engaging with the project and schoolchildren being inspired by the scientific and technological ambition of HS2."

The machines will be operated by HS2 contractor Align JV, a joint venture formed of infrastructure companies Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick.

They will be shipped in pieces and will arrive at Align JV's main site near the M25 motorway later this year.

Florence will be launched in early 2021, with Cecilia beginning the other half of the twin-bore tunnel around a month later.

Both machines are 170 metres long and have been designed for the mixture of chalk and flint they will encounter under the Chilterns.

They will run almost non-stop and are expected to take around three years to excavate the tunnel, which will be lined with concrete as they progress to near South Heath.