said it will buy back $6bn of debt raised from the Qatar Investment Authority and Saudi Arabia’s Olayan family during the financial crisis as part of a plan to reduce its funding costs. The three contingent convertible, or coco, bonds were issued in 2011 at relatively high rates of interest to help Credit Suisse comply with Swiss “too big to fail” rules, which required banks to raise large amounts of extra loss-absorbing capital. Cocos behave like bonds but convert to equity if a bank’s capital ratio falls below a pre-determined level.