Giant machines digging the first tunnels for HS2 have covered more than two miles, according to the firm building the high-speed railway.

HS2 Ltd said Florence, the first machine launched, has excavated 1.3 miles of tunnel under the Chiltern Hills, while the second, Cecilia, has made 0.9 miles of progress.

The pair of tunnel-boring machines (TBMs) are expected to complete twin 10-mile tunnels in around three years.

The 170-metre-long machines work continuously, operating as a self-contained factory cutting through a mixture of chalk and flint.

Florence was launched at a site in Buckinghamshire near the M25 motorway in May.

She was named by local schoolchildren after Florence Nightingale, the founder of modern nursing who spent many years in the county.

Cecilia, named after Buckinghamshire-born astronomer and astrophysicist Cecilia Payne-Gaposchkin, was launched in July.

A total of 10 TBMs will be deployed between London and the West Midlands for Phase 1 of the high-speed railway.