Groups opposing the Government's HS2 high-speed rail scheme will seek to derail the £34 billion project through court challenges starting on Monday.
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.
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 between the UK's two biggest cities could bring.
Two of the legal challenges are being brought by the HS2 Action Alliance (HS2AA) concerning alleged environmental and compensation consultation failings.
Another challenge comes from 51m, an alliance of councils opposing HS2 which includes Buckinghamshire County Council and Warwickshire County Council.
The 51m group says the Government's consultation was unfair and included an inadequate environmental assessment.
The High Court will also hear challenges from the Heathrow Hub group and from Aylesbury Golf Club in Buckinghamshire.
HS2AA director Hilary Wharf said: "The Government is trying to force through HS2 without following proper process. We have two strong cases coming to court that expose how the Government has been unlawfully taking short cuts in its decision-making processes. Our cases concern environmental issues and the consultation on compensation.
"We are confident in our arguments and while Government has consistently ignored the compelling case against HS2, it can't ignore the courts."