The High Court is to rule today (Friday) on legal challenges to the Government's HS2 high-speed rail scheme.
Opponents are asking a judge in London to declare in a series of five cases that the multi-billion pound project is legally flawed and must be sent back for reconsideration.
The first phase of HS2 would see a high-speed railway line running through Tory heartlands from London to Birmingham.
The scheme has polarised opinion, with many residents' groups and local councils bitterly opposing it, but supporters point out the benefits of a reduction in journey times between the UK's two biggest cities.
If successful, the legal challenge could potentially delay the scheme for years.
Judgment is being handed down by Mr Justice Ouseley at London's High Court. Whatever the judge decides, appeals against his decisions are almost certain to be taken to the Court of Appeal.
Key accusations include that the Government has unlawfully failed to undertake a strategic environmental assessment of the entire project before giving the go-ahead, or to arrange a consultation process "that allows informed responses on the true merits and demerits of the proposals".
There is also a dispute over the compensation arrangements being put in place for homeowners living near the HS2 line.
Some 172,000 properties within 1km of the first phase are reported to be affected by "a generalised blight" since the proposals were announced.