He began his career with Peat Marwick Mitchell & Co. (now KPMG), where he trained as a chartered accountant. He was appointed a partner in 1988. While at KPMG, Mr Flint specialized in banking, multinational financial reporting, treasury and securities trading operations, group reorganizations and litigation support.
In 1995, Mr Flint joined the HSBC Group as group finance director of HSBC Holdings plc.
He was chairman of the Financial Reporting Councilís review of the Turnbull Guidance on Internal Control and served on the Accounting Standards Board and the Standards Advisory Council of the International Accounting Standards Board between 2001 and 2004. He also served on the Shipley Working Group on Public Disclosure and co-chaired the Group of Thirty Report on Enhancing Public Confidence in Financial Reporting.
Mr Flint was awarded a CBE in 2006.