Rooting around the web I came across Planning Policy Guidance 16: Archaeology and planning, the document that should be informing the Secretary of State for Communities and Local Government, English Heritage and Herefordshire Council when coming to their challenging decision over the Rotherwas Ribbon.

http://www.communities.gov.uk/index.asp?id=1144057

It is certainly an interesting read when you apply it directly against the real-world case of the Ribbon.

In para 27:

As stated in paragraph 8, where nationally important archaeological remains, whether scheduled or not, and their settings, are affected by proposed development there should be a presumption in favour of their physical preservation in situ ie, a presumption against proposals which would involve significant alteration or cause damage, or which would have a significant impact on the setting of visible remains.

I do hope this clear-cut guidance for a presumption in favour is taken into account by the decision makers.

Also para 31 (Discovery of Archaeological Remains during Development):

Developers may wish to consider insuring themselves against the risk of a substantial loss while safeguarding the interest of historic remains unexpectedly discovered on the site.

Well that's Herefordshire Council (and McAlpine) sorted financially regarding any changes of plan to the road. They are insured I hope?