Henry Overman, in the most recent issue of Centre Piece, the journal of the Centre for Economic Performance, concludes that he is sceptical of the benefits of the proposed High Speed line, because the opportunity cost is high. He wonders whether this is the best way to spend government money and if there are more effective projects.

This is a conclusion that is very seductive and needs careful examination. A series of smaller projects, invested over shorter periods, offer more certainty about both their costs and their benefits. They will not be game changers and can therefore be analysed in the context of ‘business as usual’. The Eddington review also came to the conclusion that sets of smaller projects had better ratios of benefits to costs.

The proponents of large projects therefore need to be clear both about their own assumptions and those on which the conclusion above is reached.

In the UK, we undertake extensive cost benefit analysis to reach conclusions about the value of investment. These are based, as Overman points out, on values of time about which it is possible to argue both about values and the ability to work on a train. He comes to no conclusion on these issues – although they are key to the comparison of cost benefit ratios of projects by which one might conclude that small projects are better.

The opponents of High Speed 2 have, after all, made great play of the proposition that it is not ‘worth’ £17bn of taxpayer funding to save 20 minutes in getting to Birmingham. I would agree that if this were the only argument, then it does seem a rather expensive toy.

Overman goes on, however, to point out rightly that the bigger argument about HS2 is about getting to Manchester, Leeds, Sheffield and Newcastle – and indeed points further North – quicker. The argument is really about growth. This is dismissed by Overman as likely to promote growth in the South as readily as in the North. If increased growth is desirable, this might not matter of course, but in fact we know that cities with the fastest employment growth have also seen the fastest growth in rail trips and we know that better and quicker trips attract more travellers. Overman’s dismissal seems to me to be premature, especially when this is such an important part of the case.

I am disappointed that someone who has sat on the HS2 analytical challenge panel has not made some more fundamental challenges. In a stable economy we might choose to invest in transport to save people time, or to give them more pleasant journeys. When the economy needs to change and grow, we are investing for quite different purposes – to make it possible for cities to reinvent themselves and reach new markets. So we cannot compare ‘small’ projects designed for the former purpose, with large projects designed to foster growth.

The Jubilee Line Extension did not pass the cost benefit test. But Mrs Thatcher decided to build it anyway, and now it is full and has been essential to getting Docklands regeneration off the ground. Growth, anyone?

Sorry Henry – get more challenging.