“I can’t answer those questions currently,” says Lord Peter Hendy. More than 15 years have passed since the idea to build a high-speed railway up the west coast of England was first announced, and I am asking the rail minister when it will be finished. And, crucially, how much it will cost.

Only he is making it very clear that nobody knows what the final bill for Britain’s biggest infrastructure project might be. Does it concern him that the government remains committed to the railway despite this deep uncertainty? I ask. “Oh yeah, we’re dead bothered by that. Of course you would be…”

Currently tens of billions of pounds over budget and around a decade behind schedule, the Public Accounts Committee describes High Speed 2 (HS2) as a casebook example of how not to run a major project.

Reports state that the now shortened line between Birmingham and London could cost £81bn. Accounting for inflation, that would mean at least £100bn will be spent, but only 135 miles of railway built. Many people involved – from civil servants, ministers and company insiders to HS2’s original designers – have told me just how badly things went wrong.

Certainly, the project has suffered from mismanagement, misplaced optimism and failures when dealing with homeowners whose properties were in its path.