Tesco this year has seen its share price fall by 25% and eight directors have been suspended following the over reporting of profits by £250m. The Financial Conduct Authority is looking into the matter and now even the Serious Fraud office has expressed an interest in the situation. All this is on top of the premature exit of the previous CEO. How can a business the scale of Tesco and operating under close financial and investor scrutiny get itself into such a mess? How did PwC, its auditors not spot and act upon the risk of flaws in accounting?