The fate of three of Norfolk's biggest infrastructure projects could be decided at the High Court this week, as eco-activists launch a legal case to block them.
Environmentalists are trying to stop three major road schemes in the county, claiming they will make a devastating contribution to climate change.
If successful, the projects could be scrapped, or sent back to the drawing board, in a decision which could have a huge impact on other roadbuilding plans across the UK, including the Western Link, near Norwich.
The High Court case, which starts on Wednesday, concerns the revamp of the Thickthorn roundabout on the edge of Norwich, plus the dualling of stretches of the road from Blofield to North Burlingham and from Easton to North Tuddenham.
The schemes were first announced in 2014 before finally being given the go-ahead by transport secretaries last year, after recommendations by planning inspectors, following months of public hearings.
But climate change activist Dr Andrew Boswell, a former Green councillor on Norwich City Council and Norfolk County Council, launched a legal challenge, arguing the decisions were unlawful.
He argues the impact of carbon emissions from the schemes has not been properly addressed, with the cumulative effect of all of them not considered.
And, if the judge at the judicial review hearings, to be held at the Royal Courts of Justice in London, agrees the transport secretaries' decisions were unlawful, it could prevent the schemes going ahead.
The hearings are expected to last two days, although a verdict on whether the decisions were lawful or not is likely to be some weeks or months away.
The challenge has meant National Highways - the government company with responsibility for major A roads including the A47 - has not been able to begin construction at the three locations.
READ MORE: New report into full dualling of A47 in Norfolk commissioned
A spokesperson for National Highways said: "We know from speaking to local people there is overwhelming support for these schemes by those that recognise the safety case to improve this very busy road.
"We stand by our plans and remain confident they can deliver significant improvements to both safety and congestion on the A47 as well as a providing a significant boost to the regional economy."
But Dr Boswell, who has raised £50,000 towards his legal fees, including through a crowdfunding campaign, said his challenge could serve as a "litmus test" over the government's approach to road-building.
He said: "The case has become very important on the road transport front, not just in terms of Norwich and Norfolk, but nationally, in terms of how cumulative carbon assessments are not being assessed.
"I think it will be a litmus test and I hope the court gets a sense of the wider picture, as that is much bigger than just these cases."
Dr Boswell had also intended to argue the licensing relating to the Norfolk super-colony of barbastelle bats near the North Tuddenham scheme was not done correctly, but that aspect of his challenge has been dropped.
What are the A47 schemes at the centre of the legal challenge?
The A47 schemes were originally announced in 2014, by then prime minister David Cameron.
There was £300m earmarked for Norfolk schemes, along with other improvements in Cambridgeshire.
Mr Cameron had said work would start by 2020, but the three biggest Norfolk projects were only granted development consent last year.
The plans for Thickthorn include a new slip road off the A11 northbound, which will take motorists beneath both roads before re-joining traffic on the A47 heading towards Great Yarmouth - eliminating the need to use the roundabout.
The changes would also see a segregated left-hand turn added to those travelling eastbound on the A47, a new footbridge and a fourth lane on the southern part of the junction.
Just over 1.6 miles of the road between Blofield and North Burlingham - considered a crash blackspot by police - are due to be dualled.
And five-and-a-half miles of the road between Easton and North Tuddenham are also due to be dualled.
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