It is sometimes in the smallest things that we find the insights that allow us to understand the largest. For investment banks, the collapse of Invexstar Capital Management last year must be one of those moments. Invexstar had capital of less than £1 million, yet at the point of its failure in May 2015 the London-based hedge fund had been given credit lines by five banks, including BNP Paribas, Nomura and Morgan Stanley, to trade government bonds worth more than £2 billion. If these figures were not astonishing enough, Alberto Statti, the firm’s manager, was not even registered to trade, something that all five banks appeared to miss. Not only this, but the Italian financier had what an employment tribunal described this month as a “chequered history”, with Companies House records showing he had already presided over two failed funds — a record that also seemed to elude the banks.