A large hole has opened up above one of the tunnels built for the HS2 high speed rail line.

A spokesperson for HS2 Ltd said that the hole near Little Missenden, Buckinghamshire, was above part of the Chiltern tunnel and that the company had notified the Environment Agency and were engaging with the landowner.

They added that investigations were ongoing but that the opening was probably linked to “pre-existing ground conditions”.

Campaigners against HS2 have said that the hole, which they have measured as being about six metres in diameter and five metres deep, showed that it was “time to stop digging”.

The 16-kilometre Chiltern tunnel is the longest on the HS2 project. HS2 Ltd said the site had been sealed off and "there is no risk to the public".