This was the week that the rookie National Infrastructure Commission earned its spurs. The Chancellor embraced the NIC's reports on Crossrail 2 and transport in the north, and so Andrew Adonis has succeeded in making more progress with government in one week than Sir Howard Davies managed in almost a year.
But while a decision on airports continues to languish with No 10, Crossrail 2 has acquired what looks like unstoppable momentum. The Chancellor's decision to apply his personal seal of approval to the scheme – courtesy of a pre-Budget visit to the Tottenham Court Road interchange of Crossrail 1 with Crossrail 2 – is particularly crucial, as this will electrify civil servants who require strong political leadership for a project of such magnitude.
However, the experience of Crossrail 1 should remind us that we are not there yet. If we are to avoid the 40-odd year hiatus suffered by Crossrail 1, then this week's support must be capitalised upon, not banked. The much lauded "green light" should be seen as encouragement to race ahead to the next checkpoint as quickly as possible, not yet as a final signal to proceed. So what now?
First, the project needs to be gripped and championed by the next Mayor, so that the government's "aim" of depositing a Bill within this Parliament becomes reality. With Parliamentary managers suffering from HS2 fatigue, securing a legislative slot will be no easy feat, but is vital to enabling construction to start in the early 2020s.
Second, London needs to listen and respond to the challenges laid down by both the NIC and HM Treasury. That means exploring options for reducing and phasing costs, and developing a funding package that sees London shouldering at least half of the cost of the scheme.
Get these right and Crossrail 2 can be a defining part of the next Mayor's legacy.