The earthwork known as Grim's Ditch stretches in sections across the Chilterns for a total of 18 kilometres. It is believed to date from the Bronze or Iron Age, but this is uncertain because it has never been seriously excavated.

Archaeologists agree, though, that it is an important earthwork – which is why it is Scheduled as an Ancient Monument.

‘Scheduling’ gives an archaeological site the highest level of protection that the state can give. But the ‘Hybrid Bill’ that is going before Parliament to enable the construction of HS2 allows previous protective legislation to be set aside. If the HS2 plans go ahead a 120-metre section of Grim's Ditch will be destroyed.

The planned route of HS2 cuts across a section of Grim's Ditch in the Misbourne Valley between Wendover and Great Missenden. Not only will this be destroyed, but the path of the ditch across fields to the north-east – a further 350 metres of potential buried archaeology – is planned as an HS2 spoil heap. The heavy earthmoving equipment will just as surely destroy what is left.

The significance of Grim's Ditch is twofold: first in the way its initial construction reflected territorial land divisions in the Chilterns in the first millennium BCE, and secondly in the effect it has had on the surrounding landscape, agriculture and settlement over almost 3,000 years of history.