The first 2,000 tonne tunnelling machine passed the one mile mark this week during the construction of the first tunnels for the controversial HS2 line underneath the Chiltern hills.

Launched in May, the 170m long Tunnel Boring Machine (TBM) covered the first mile cutting through a mix of chalk and flint beneath the Chiltern hills just outside London.

Named ‘Florence’ by local school children, the TBM is one of two identical machines excavating the twin ten-mile-long tunnels. A second machine, named ‘Cecilia’ is a short way behind, with both TBMs expected to break out in around three years’ time.

In what will be a painful watch for anti-HS2 and environmental campaigners, a video released by HS2 Ltd shows what the tunnel under the precious Chilterns looks like so far.

Designed specifically for the geology of the Chilterns, each machine is a self-contained underground factory, digging the tunnel, lining it with concrete wall segments and grouting them into place as it moves forward.

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

A crew of 17 people keep the machines running, working in shifts and supported by over 100 people on the surface, managing the logistics.

Each of the separate northbound and southbound tunnels will require 56,000 precision engineered, fibre-reinforced concrete wall segments – which are all being made at the south portal of the tunnel, next to the M25.

During her first mile, Florence and her crew have installed more than 5,500 separate segments, each weighing around 8.5 tonnes.

Approximately 2.7 million cubic metres of material will be excavated during the construction of the tunnels and used for landscaping around the south portal site.

In total there will be ten TBMs on the HS2 project - working to create 64 miles of tunnel between London and the West Midlands including major tunnels on the approach to London and Birmingham.

The TBM is named after Florence Nightingale, the founder of modern nursing, who spent many years in Claydon, Buckinghamshire where she wrote books on nursing, with the name suggested by students at Meadow High School in Hillingdon.