By Natasha Brereton LONDON -(Dow Jones)- Bank of England Governor Mervyn King said Tuesday that heightened regulation can’t prevent the financial speculation that results in bank failures, and called for a serious review of the structure of the banking sector whose goal would be to eliminate institutions that are too important to fail. In a speech to business people in Scotland, King championed the idea of separating banks’ utility functions as a means of minimizing the government’s effective subsidy of risky activities and reducing the U.K.’s reliance on a small number of very big banks. Turning briefly to the economy, he noted that there was likely to be “significant” fiscal tightening in the years ahead, and stressed the need to boost broad money growth, but gave no clear indication on whether he would favor extending the bank’s bond buying policy. “The sheer creative imagination ...