English Heritage, Historic England and The National Trust contend that a short tunnel at Stonehenge would be a net improvement and therefore justified. But now UNESCO has delivered a very clear no:

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“It is not considered satisfactory to suggest that the benefits from a 2.9km tunnel to the centre of the property can offset significant damage from lengths of four lane approach roads in cuttings elsewhere in the property…. The potential impact of some 2.2km of four lane approach roads in cuttings on the Stonehenge landscape could fundamentally compromise the OUV of the property….. The World Heritage Committee….Urges the State Party to explore further options with a view to avoiding impacts on the OUV of the property, including: (1.) The F10 non-tunnel by-pass option to the south of the property, (2.) Longer tunnel options to remove dual carriageway cuttings from the property and further detailed investigations regarding tunnel alignment and both east and west portal locations;

They appear to have deliberately left zero room for argument – for in 2015 the Government stated: “the UK Government has committed to working closely with UNESCO and its advisors ICOMOS throughout this process”. That surely means they wouldn’t and couldn’t defy UNESCO on a central matter of principle?