BBC News spoke to key government figures, scientists and health officials involved from the start.
"Automotive is nothing if not determined, adaptable and resilient, yet, as the clock ticks ever closer to midnight on Brexit negotiations, the competitiveness and employment we need get back to growth - green growth - hangs in the balance," said the group's chief...
It's about more than just tweaking numbers. It'll give us some idea of who might get a pay cut, what areas the government wants to invest in, such as schools, hospitals and roads.
Black Friday emissions boom predicted