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By contract design, the overall financial system became impossible to decompose into separable sub-structures. Such a structure is in fact worse even than Tempus’s complex production line. Structured credit was equivalent to taking one part randomly from each of 1000 watches and reassembling the pieces. No watchmaker in their right mind would expect the resulting timepiece to keep time for too long. Such was the CDO story. However sensible structuring of credit may have seemed for individual firms, it is difficult to conceive of a network which could have been less structurally robust. Darwinian evolution is currently in the process of naturally deselecting CDOs. But there is a strong public policy case for the authorities intervening more aggressively when next financial innovation spawns species with undesirable physiological features. Finally, the business strategies of financial firms have over the past decade created a network structure which is much less easily decomposable. Under the old financial order, mutuals were a sub-structure, as were commercial banks, investment banks and investment funds. In some cases that was by choice. In other cases it was the result of regulatory  38  President’s Working Group (2008). 39  For example, as proposed in King (2008). BIS Review 53/2009  17  design: for the larger part of the past century, the Glass-Steagall Act in the US prohibited inter-breeding between commercial and investment banking. Deregulation swept away banking segregation and, with it, decomposability of the financial network. The upshot was a predictable lack of network robustness.