A dozen years ago, I went to the London office of Credit Suisse for a tutorial about so-called “cocos” — or the contingent convertible bonds introduced after the 2008 financial crisis, in a bid to enable banks to absorb losses in a crisis. The CS financiers duly presented a neat PowerPoint, complete with arrows and charts, which explained that cocos lay second from bottom in the capital structure. Thus if a bank went bust, its equity would be wiped out first, followed by the cocos, in order to protect senior creditors. In exchange for this risk, those bonds paid a high (ish)