HS2: Aerial pictures show large hole above rail tunnel
Aerial pictures show the extent of a hole that has opened up above a tunnel built for the HS2 high-speed rail line.
The drone footage was recorded near Little Missenden, Buckinghamshire, above part of the Chiltern tunnel.
Campaigners against HS2 said the hole, which they said measured about 6m (20ft) in diameter and 5m (16ft) deep, showed it was "time to stop digging".
HS2 Ltd said it was engaging with the landowner and had notified the Environment Agency, but the site posed "no risk to the public".
A spokesman added that investigations were ongoing, but it was likely linked to "pre-existing ground conditions".
The 10-mile (16km) Chiltern tunnel is the longest on the HS2 project, which is designed to improve transport links between London, Birmingham and the north of England.
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