Earlier this month, I asked the leaders of a group of US-based companies what - if anything - they were doing to prepare for "Grexit", or a possible exit of Greece from the eurozone. The responses from the manufacturers were rather vague.

The bankers, however, were alarmingly precise: amid all the speculation about Grexit, they told me, banks are increasingly reordering their European exposure along national lines, in terms of asset-liability matching (ALM), just in case the region splits apart. Thus, if a bank has loans to Spanish borrowers, say, it is trying to cover these with funding from Spain, rather than from Germany. Similarly, when it comes to hedging derivatives and foreign exchange deals, or measuring their risk, Italian counterparties are treated differently from Finnish counterparties, say.

The halcyon days of banks looking on the eurozone as a single currency bloc are over; cross-border risk matters. To put it another way, while pundits engage in an abstract debate about a possible break-up, fracture has already arrived for many banks' risk management departments, at least when it comes to ALM in their eurozone books.

It is difficult to overstate the significance of this, or the potential hidden costs. As a report from the European Central Bank last month notes*, until 2007 the eurozone seemed to be on a glide path towards steadily rising levels of financial integration, which was delivering big economic benefits, by cutting the cost of capital.

David Fuller's view Whatever one thinks about the entire euro project, and I speak as one who wanted the UK to retain control of its monetary policy and not join the single currency, I am very much of the view today that Europe should stick with the programme and declare its intent to push rapidly for full fiscal union. I see this as infinitely preferable to a break-up of the single currency which would send shock waves well beyond the Eurozone.

The asset-liability matching (ALM) process is another serious warning for the Eurozone which is a rudderless ship at the moment in terms of any cohesive leadership. The International Monetary Fund, World Bank and especially the European Central Bank should spell out the deleveraging risks for GDP growth, in addition to what we have already seen.

I commend the rest of Gillian Tett's column to you, not least the concluding paragraph.