The inquisition of the bankers gives rise to many fascinating points which we may pick up in future, but for now here's one I just can't resist. Their risk management systems were all excellent, of course; they all discussed risk ad nauseam in their Board meetings, they all did their stress-testing etc etc, but no-one foresaw ... in particular, no-one foresaw the  Lehman collapse.
Well, obviously no-one that matters but, ahem, this from October 2007:
"Stress Tests - one problem is paucity of imagination: the worst we can envisage is what has happened before. When oil was last at $10 (1998!), very few companies were stress-testing for $80 ... who is modeling the collapse of a really big bank now?"
Modesty forbids ...