The Government was, no doubt, preparing to shrug off criticism of HS2 from its backbenchers, and even ministers, if their constituents were so up-in-arms that the MPs bore little choice as elected representatives other than to speak up for their voters.

But the doubts about the project outlined by Mayor of London Boris Johnson, pictured, could be harder to ignore.

As is the case for the Conservative MPs opposed to the project, it seems to be the proposed route that is the biggest problem for Johnson, rather than, say, the cost or philosophy behind the project.

He called the current proposal “inadequate for a number of reasons”, especially because of the lack of environmental mitigation and because he wants the sections running through London to run through tunnels. He also said not enough is being done to compensate for the extra demands on Tube capacity to cater for the extra passengers who will be travelling to and from Euston once HS2 opens.

The Government has made perfectly clear that it is committed to HS2, but could be more open-minded on some of these specific details. Unsurprisingly, what Johnson asks would cost a lot more money, and with the cost already so high and the subject of so much critical comment, ministers may rather ignore his concerns to try to keep costs where they are.