Groups seeking to stop the Government's HS2 high-speed rail scheme are taking their fight to the High Court today.
The first of a series of legal challenges to the £34 billion project will begin this morning and will go on for several days.
If the judicial reviews are successful, the Government might have to run its HS2 consultation process again, potentially delaying the project by up to two years.
A decision on the reviews may not come for several weeks.
The first phase of HS2 would see a new, high-speed railway line running through Tory heartlands from London to Birmingham.
The scheme has polarised opinion, with many residents' groups and some councils bitterly opposing it, but supporters point out the benefits a reduction in journey times.