Two tunnelling machines bought to help build HS2 have been unveiled by the firm behind the high-speed rail line.
The excavators will bore a 10 mile (16km) tunnel through part of the Chilterns, from a site near the M25 to near South Heath in Buckinghamshire,
HS2 Ltd chief executive Mark Thurston said the machines would “be a defining moment in the history of HS2”.
But campaigners said HS2 was “decimating countryside and creating a huge financial burden”.
The two 2,000-tonne machines, built at a factory in Germany, will dig as deep as 80m (262ft) below ground.
They have been named Cecilia and Florence, after Buckinghamshire-born astronomer Cecilia Payne-Gaposchkin and Florence Nightingale, following a public vote from a shortlist of suggestions made by local schoolchildren.
Florence will be launched in early 2021, with Cecilia beginning the other half of the tunnel about a month later.
Both machines are 170m (558ft) long and have been designed for the chalk and flint under the Chilterns.
They will run almost non-stop and are expected to take about three years to excavate the tunnel, which will be lined with concrete.
