T he Barclays boss CS Venkatakrishnan, having seen the bank hit in the space of six months by two high-profile blow-ups in the world of shadow banking, is pledging to take more care. “We are constraining lending to certain structured finance counterparties who operate more vulnerable business models and cannot convince us of the quality and independence of their financial controls,” he said . There’s an obvious response to that vow of greater vigilance: what were you doing previously? Wouldn’t it have been a good idea in the first place not to lend to high-risk outfits with unconvincing financial controls – for example, those with large mortgage exposures but small audit firms? There was, in other words, a sense in the chief executive’s comments of stable doors being shut rather too late. But here’s the other point about Barclays’ twin embarrassments: they are significant but not enormous in the grand scheme.…