A campaign against the building of a road tunnel past Stonehenge has been backed by a trio of historians.
A £2bn proposal, which includes a 1.8-mile (2.9km) tunnel, was announced by the government in December, aimed at easing congestion on the nearby A303.
Dan Snow, Ruth Scurr and Tom Holland have now united with Stonehenge Alliance to oppose the plans, which they say "endanger" the ancient site.
But, the Department for Transport (DfT) said safeguarding it was essential.
"Stonehenge is one of Britain's greatest treasures and it is important to note that English Heritage and National Trust support our plans," said a DfT spokesman.
"It is essential that we ensure this site of cultural and historical significance is safeguarded as we progress with the upgrade.
"As with any road scheme, we will consult with interested parties before any building begins on the A303."
A similar scheme for the route, which links London and the South West, was dropped several years ago because of the cost.
However, there are growing concerns over congestion on the A303 which has been described as "highly detrimental" by English Heritage, which manages the monument.
But Stonehenge Alliance campaigners want "no further damage" to the world heritage site, which totals around 25 sq km (9.6 sq m) of chalkland, according to UNESCO.
Joining with them, Mr Snow - president of the Council for British Archaeology - said: "Of all our many treasures on these islands, none is more internationally revered than Stonehenge.
"We have recently started to realise that the standing stones are just a beginning, they sit at the heart of the world's most significant and best preserved Stone Age landscape. The government's plans endanger this unique site."
Ms Scurr added the proposal to widen the A303 would have a "destructive effect on the surroundings", with Mr Holland suggesting the battle against the plans was "an unending one".
Both English Heritage and the National Trust have given their support to the option of "the longest tunnel possible".
The director of the National Trust, Dame Helen Ghosh, and chief executive of English Heritage, Dr Simon Thurley, said no decisions had been made yet on possible locations, road alignment or design.