When you or I decide whether to spend a huge amount of money on an extension, we ask ourselves these questions:
Can it be done?
Do we need it?
Can we afford it?
These questions would have been racing through Boris Johnson's mind as he weighed up the pros and cons of HS2 this winter. But there was something else, something bigger: cold, hard politics.
Let's start with the first, and most pressing bit of politics in this part of the world. The Conservative Party is very proud of the fact that the Mayor of the West Midlands is one of their own. On paper, the West Midlands - traditionally a Labour area - might have followed Manchester and elected a powerful Labour Mayor. But in 2017, Andy Street triumphed. It was hugely symbolic. This year, that post is up for election again. Labour has just selected its candidate. The campaigns are getting into full swing ahead of polling day in May. The Conservatives are desperate to press home their advantage in the Midlands by retaining the Mayoralty.
Andy Street has always been a vocal supporter of HS2. What message would it have sent to voters if the PM had ignored the Mayor and scrapped the project? One of Andy Street's best selling points has always been that he has the ear of Government. Had he not been able to get his own way on this flagship project, it would have left him looking weak. Now he can say to voters "look at what I have achieved!". He has faced down powerful opponents like the Prime Minister's infamous advisor Dominic Cummings, and won. When it comes to perceptions, whether the voters think HS2 is good or bad becomes almost irrelevant. What is really important is to project the image of an influential and powerful Mayor, and with this decision, Boris Johnson has allowed Andy Street to play that role in the coming election campaign.
But what of the other political pressures pushing Boris Johnson to approve HS2?
If you listen to the national political pundits, this is all about the PM repaying the Midlands and the North for helping him win the General Election. It is about proving to the new ex-Labour, pro-Brexit Tory voters in places like Stoke, West Brom and Ashfield that he is delivering for them, in the regions. "No longer are the provinces left behind". But I don't buy that analysis. If anything, ploughing on with HS2 risks losing those voters. Spend an hour or two talking HS2 with people on the streets of any Midlands town, and you will find no shortage of hostility.
ITV News Central's own research in partnership with YouGov last year also pointed towards what the anecdotes and the vox pops suggest: there is a lot of consistency between those who support Brexit, and those who oppose HS2. It's also reflected in longstanding political opposition from UKIP, the Brexit Party, and many Brexit-leaning Tory backbenchers. In other words, the very voters who propelled Boris Johnson back to Downing Street.
Why? Unless you live close to one of the three Midlands stations, it is a struggle to see the benefits of HS2. For some areas, HS2 represents nothing more than a crash in house prices and years of heavy construction work at the end of their road. And further afield, it is seen as an expensive project for people who live in the big cities; another example of London spending taxpayer's money on something for the elites, and not for them. It's a sentiment which the Leave campaign, Nigel Farage, and ultimately Johnson himself has found to be a powerful vote-winner.
This is exactly why the Government is promising big investment in local transport links alongside the HS2 announcement today. Boris Johnson knows that without a nod to bus services in smaller towns, and train links for far-flung commuters, his image as a man of the people would be at risk. Again, it's all about the politics.
But there was also a big political risk to stopping HS2. The business community in Birmingham and in the East Midlands would have been furious. There would have been job losses. Regeneration projects would have ground to a halt. Images of abandoned construction sites in Birmingham, while London continued to boom, would not have been a good look. And there was something else. Boris Johnson's track record shows he is fond of the big infrastructure projects. He is even fonder of things which leave a lasting personal legacy. HS2 is certainly both of those things.
But if he was going to do it, he had to do it now. His political capital won't last forever. The General Election win in December was a very personal victory. I lost count of the number of Labour voters who told me they were voting "for Boris". Not the Conservatives ... "Boris". While he continues to bask in victory, while his new backbenchers are personally grateful to him for their jobs, he can take the gamble.
That's not to say the road won't be rocky though. Incredibly, so soon after a landslide election win, it is conceivable that Boris Johnson could see a sizeable rebellion amongst his MPs, and even a Commons defeat on HS2 legislation. Lichfield MP Michael Fabricant told Radio 4's Today programme that he would rebel in any vote. Some estimates suggest there are as many of 60 colleagues who share that position.
As with Brexit, Boris Johnson now has full ownership of the HS2 project. And like Brexit, its success .. or failure will help to shape his term in office, and his legacy.