The second reading of the Hybrid Bill for HS2 is expected to take place in Parliament this evening , and MPs are expected to vote on the project at around 10pm.
After the second reading, people have just under a month to hand petitions asking for mitigation from the High Speed line to Parliament, businesses even less time.
Local MPs, residents' associations, community groups and individuals will be petitioning, and Mayor of London Boris Johnson has said he will be joining those asking to extend the Northolt tunnel, which under current plans will come over ground at a portal in West Ruislip.
Ruislip Against HS2 chairman Lottie Jones was told of Mr Johnson's petition plan at a meeting with Transport for London on Friday.
She was told his decision was made very recently, after she questioned him over the HS2 Heathrow spur while he was in Uxbridge to unveil his plan for the future of Heathrow Airport .
At the time the Mayor said the spur to the airport, connecting to the HS2 line in Ickenham, would be a 'ludicrous waste of money'.