This spending review is a massive deal. It's a massive deal because of the sums of money and capital the government is about to allocate - 拢600bn over the next three to four years.
But it is also a massive political moment as the Labour government tries to turn the corner on a difficult first year and show voters it can deliver the change it promised.
It is not, say No 10 insiders, another reset - but rather a chance to show "working people" why they voted Labour. Look at the blitz of announcements over recent days, and this is a government trying to sell the story of renewal.
In total, there will be 拢113bn of additional capital investment, which the government will frame as the long-promised "decade of renewal" around the three pillars of security, health and the economy.
But that is only one half of this spending review and only one half of the story we will hear today.
That's because the largesse of the capital investment will be matched with spending settlements for day-to-day spending across Whitehall that will draw into sharp relief the choices and priorities of this government.
Security and health are two of her pillars, and it will be defence and health that will take a bigger share of the spending pot.
One to watch is the Home Office, where the home secretary was the last to hold out on a settlement and seems to have had it imposed on her by the chancellor.
Watch too for a squeeze on council budgets as the chancellor uses her capital budget to invest in housebuilding, while day-to-day spending is squeezed across our councils, schools and courts.