Diamond headed Barclays' bid to purchase Lehman Brothers in September 2008, but that was stymied by the Bank of England, thereby avoiding Barclays buying an investment bank that was later known to be bankrupt. Diamond then sealed an agreement with Lehman Brothers President and COO Bart McDade to purchase key assets of that firm after it filed for bankruptcy, which instantly gave Barclays an investment banking foothold on Wall Street. Diamond became deputy group chief executive on October 1, 2010, and then succeeded John Varley as Group Chief Executive on January 1, 2011.