Prime Minister Boris Johnson, Chancellor Sajid Javid and Transport Secretary Grant Shapps are meeting to discuss whether HS2 should be built.
Here are 11 key questions about the controversial high-speed rail project.
– Do the Conservatives support HS2?
The party is split on the issue. Chancellor Sajid Javid is set to back the project, but the Tory benches erupted into shouts of “No” during Prime Minister’s Questions when Mr Johnson was asked if he agreed that HS2 should go ahead.
Mr Johnson’s most senior adviser, Dominic Cummings, is said to be in favour of scrapping the scheme.
– What was its original expected cost?
The project was allocated £56 billion in 2015.
– What is the latest estimate?
A widely leaked review by Douglas Oakervee found it could cost up to £106 billion.
– How much money has already been spent?
HS2 Ltd has spent around £8 billion. The money has gone towards the purchase of land and property, ground investigation work, technical designs, IT systems, wages and public engagement.
– What about the timetable?
The first phase between London and Birmingham was due to open in 2026, but services between the cities are now forecast not to start until between 2031 and 2036.
– What has gone wrong?
Whitehall spending watchdog the National Audit Office found that the project is over budget and behind schedule because its complexity and risks were under-estimated by the Department for Transport and HS2 Ltd.
– Who is in favour of HS2?
Political leaders in northern England and business groups claim the railway is vital to boost transport links across the region, providing increased capacity on an overcrowded network.
Construction firms warn that scrapping HS2 would cause major damage to the industry.
– Who are its opponents?
Several environmental groups claim building HS2 would cause huge damage to natural habitats, including dozens of ancient woodlands.
Communities living on or near the route have expressed anger at the impact on their lives, while many people have said the project is simply too expensive and the money would be better spent elsewhere.
– What is the planned route?
Phase 1 is planned to run between London and Birmingham.
Current designs involve a second Y-shaped phase launching in two stages: Phase 2a from the West Midlands to Crewe followed by phase 2b from Crewe to Manchester, and Birmingham to Leeds.
– What impact would HS2 have on journey times?
Examples given by HS2 Ltd include Manchester-London journey times cut from two hours and seven minutes to one hour and seven minutes, and Birmingham-London trips reduced from one hour and 22 minutes to 45 minutes.
– When will a decision be made?
The Prime Minister told the Commons on Wednesday that a decision will be made “very shortly”.
Neil Lancefield is PA Transport Correspondent.