Mr. Robert Chote:

We do not have any role in that. The Government sets out plans for departmental capital so that would be mostly departmental capital spending with some resource current spending.

Implicitly, it has set out plans through to 2019-2020, and indicative plans for a bit further ahead for the Department of Transport. If this thing has to be built it will take a chunk out of the Department of Transport's budget and some of the rest of the budget might not be so finely detailed, leaving members with the task of drawing conclusions as to what is left to spend on other things. We would not want to focus on that because, historically, the Treasury sets limits for public expenditure in those sorts of areas, sometimes moving them if it thinks it has more or less money to play with, but it tends not to break them by mistake. We take what it says about the aggregate capital budget, which would include something like HS2, and reach a judgment whether, given the near-term information, it is likely to overshoot or undershoot this year and in other years years for which it has plans. We would not, however, say that we think HS2 will overrun by 50%. If we did reach that view - and this is possible given that we are fundamentally concerned about the state of the public finances - the question would be whether to borrow more or spend less on something and that, ultimately, is a political decision, not an economic one.