A TUNNEL beneath Stonehenge would obstruct views of the sunset at the winter solstice and destroy the whole meaning of the ancient monument, according to campaigners.

Opponents say the light from cars would create a permanent glow, ruining the “last flash”, the period when the sun dips below the horizon.

Under current plans, the 1.8mile tunnel would emerge in the line of sight of those celebrating the shortest day of the year at Stonehenge on December 20-21 – an important ceremony for Druids and Pagans.

Amesbury Museum and Heritage Trust chairman Andy Rhind-Tutt said: “If they are going to put a tunnel in and it came out where they are exploring at the moment, then you’re going to have this glow coming off the ground as the sun sets, so it would destroy the whole purpose and meaning of Stonehenge.”

A dig is taking place half a mile from the stones, which will shed light on the impact of such a tunnel on the surrounding area.

Highways England said the dig was just one of a wide range of surveys in the pipeline.

A spokesman said: “Since we last met with the communities earlier in the year, we have been working hard to make sure we fully understand the benefits and potential impacts of upgrading the A303 past Stonehenge.

“Based on our work so far, a tunnel is our working assumption, but we have to remain open-minded and are still evaluating all options to improve the road.”

A UNESCO report published in May backed the plans but said any tunnel must protect the outstanding universal value of the site and benefit road users.

English Heritage also supports the tunnel, but only if it is “designed and delivered well”.

Mr Rhind-Tutt added: “No matter how well designed, a dual tunnel will not cope with seasonal demand, especially with a junction near its portal and the structure won’t last more than 125 years.”

“If Highways England carry on regardless, their lasting legacy will be a tunnel that doesn’t fit the purpose, massive maintenance costs, destruction of the place where British history begins, no solution to South Wiltshire traffic problems and no way of altering it without completing the destruction of a world heritage landscape.”

Druid and campaigner King Arthur said: “One of the issues that this is going to come down to is money, and I think it is a silly idea to have the portal there.”

Consultation on the plans will begin early next year.