It was a gift for opponents of the planned HS2 fast rail link connecting London with the Midlands and the north. A suppressed government report showed that the Department for Transport thought the £50bn project was unaffordable given other spending commitments.

This embarrassing finding was sneaked out on the day that the government shunted into the sidings promised upgrades of rail lines in the Midlands and the north. Inevitably, the conclusion drawn was that the delays to the electrification of the London-to-Sheffield and Manchester-to-Leeds lines are the unacceptable price being paid for the mounting cost of HS2, a worthy successor to Concorde in the long list of great British white elephants.

In truth, there is no link between Network Rail’s failure to deliver on its five-year investment plan and the billions being budgeted for HS2 over the next couple of decades. Not yet, at least. But the cost overruns and the missed targets that have led to the transport secretary Patrick McLoughlin “pausing” the electrification upgrades provide little optimism that HS2 will be brought in on its current budget, or anything like it. And, eventually, that would have an impact on transport spending elsewhere.

Yet, before HS2 is written off as a extravagance Britain can’t afford, it is worth putting the case for a new high-speed rail line.

The argument is not about cutting half an hour off journey times for business men and women, since they all work on the train anyway. It is not about modernising the nation’s rail network, although, given the UK’s lowly ranking of 27th in the World Economic Forum’s league table for the quality of infrastructure, there is plenty of room for improvement. Opponents of HS2 are not opposed to spending more on the railways: they simply think that the money could be spent better elsewhere, on smaller and less glamorous projects.

It is not even about the way in which the northern regions of England have received disproportionately low levels of transport investment, both in comparison with London and regions in other European countries.

No, the real argument in favour of HS2 is that it could transform the economies of the Midlands and the north, acting as the catalyst for faster growth in the way that a hundred piecemeal projects could not.

This is what might be called the “build it, they will come” approach, named after the film Field of Dreams, in which Kevin Costner builds a baseball stadium in the US midwest because he is convinced the crowds will turn up. They duly arrive.

But that’s just Hollywood. Is there any evidence that “build it, they will come” works in the real world? Perhaps surprisingly, there is. A recent study of Berlin during the period 1880-1914 that saw the building of its public transit system found a “mutually dependent relationship between local economic performances on the one hand and transportation supply on the other”.

Put a different way, it wasn’t simply the growth of Berlin that led to the development of its public transport system. It was the investment in the public transport system that led to the growth of Berlin.

There are more modern examples of the same phenomenon. Canary Wharf, in what used to be London’s docklands, is one. The development around the Guardian’s offices in King’s Cross, London, is another. A big-bang approach with large-scale investment can lead to rejuvenation and rapid growth.

The economic performance of cities matters. They have higher productivity and lower per-capita carbon dioxide emissions than non-city areas, which means the imperative is to to make cities denser and more easily accessible from surrounding areas.

A report by the consultancy Volterra* found that infrastructure projects can be game changers for both regions and the entire country, but only if there is a re-jigging of the way schemes are evaluated.

“The UK’s current appraisal and funding system is based on the assumption that transport investments are made to generate welfare improvements for passengers, rather than to change the economy’s output potential. Where change is only incremental it may well be reasonable to consider the economy as being independent of transport in this way. However, where there is the potential for structural economic change, accompanied by major spatial change locally and regionally, this is unlikely to provide a sufficiently full view of likely future transport requirements.

“The changes experienced at Canary Wharf show that past trends are not a useful guide to the future in all circumstances.”

Britain has rarely, if ever, approached infrastructure in this way. There has been no assessment of what is actually needed, no overall vision, no guaranteed long-term funding. Instead, money has been thrown at individual projects for political reasons, capital spending has borne the brunt of cuts to public spending, management has been poor.

The five-year delay in making a decision about airport capacity is an example of economic decisions being coloured by political cowardice; the railways a tribute to the make-do-and-mend approach; the intermittent stretches of dual carriageways on major (non-motorway) roads the result of money running out. The inadequacies of the transport system are a big part of the UK’s productivity problem.

Fair enough, opponents of HS2 might say, but that still falls short of a compelling reason for spending £50bn (and the rest) on a railway line, especially since the opportunity cost, upgrades and new investment that won’t happen, is potentially high.

That’s a reasonable point. The argument for HS2 is that it could provide the catalyst for growth in the Midlands and the north. To that extent, George Osborne is justified in talking about the need for a northern powerhouse.

But it will only work on certain conditions. First, control over transport has to be de-centralised in the way that it is in other countries. It is no accident that the two regions of the UK that have the most local control over transport – London and Scotland – have the highest spending per head.

Second, the management of projects has to be improved – something that a more localised approach should help deliver. Third, HS2 should be built from the north southwards rather than from London northwards. That would both maximise the benefits to the northern regions and bring them forward in time. Fourth, any overruns on HS2 should not result in raids on the rest of the transport infrastructure budget.

Those who see HS2 as just another vanity project will say this is pie in the sky and that the chances of transforming the northern regions lie somewhere between slim and nil. This looks unduly pessimistic. In the right circumstances “build it, they will come” could work. But if HS2 is to be scrapped, it should be scrapped now rather than when billions of pounds have been spent on it.

*Investing in City regions: Volterra