This is Iain Martin’s weekly newsletter, exclusively for Reaction subscribers. After writing a book a decade ago about the financial crisis – and the rise and fall of RBS, once Royal Bank of Scotland, now NatWest – I was asked many times at book festivals and in interviews to define the main lesson.  Was the crash primarily a story of greed? There was some of that, of course, because human beings were involved and greed is a more than occasional  feature of human behaviour. Why did no-one go to jail, other than a few traders jailed wrongly, it now appears, in the unrelated Libor scandal? The answer is almost everything that was done, no matter how annoying or bewildering, was legal.