Former ANZ senior executive David Stephen will make a comeback to Australian banking at Westpac next year.Stephen, who has been a senior executive at Royal Bank of Scotland since 2013, will take over as Westpac's chief risk officer from Alexandra Holcomb.Holcomb, who yesterday announced her retirement after 21 years at Westpac, has been CRO since 2014.The appointment of Stephen is controversial in light of his sudden departure from ANZ at the height of the Opes Prime share lending debacle in August 2008.A review of ANZ's involvement in the scandal by the former head of KPMG Australia, David Crawford, identified cultural and risk management failures in the bank's securities lending business.Crawford found the bank lacked a clear understanding of securities lending and did not act on shortcomings in the business unit that were identified by several internal audits.ANZ eventually dished out more than A$200 million to compensate Opes Prime creditors after the liquidator initiated legal action against the bank.ANZ announced on 22 August 2008 (the same day that the findings of Crawford's review were announced by then chief executive, Mike Smith) that Stephen and five other managers and executives were leaving the bank."The review committee found weaknesses in the management and oversight of the equity finance business within ANZ's securities lending unit," said Smith at the time."Taken together, this meant that ANZ did not adequately identify and manage the range of risks which arose from the operation of a business of this nature."Smith also stated: "A range of other management accountability issues associated with the operation, management and oversight of the equity finance business were also identified. As a result, ANZ has taken action involving a number of employees. This includes formal notes placed on employment records, cuts to remuneration and the departure from ANZ of six managers and executives."Stephen spent four years at ANZ in various risk management roles before he was promoted to chief risk officer in 2007.Since October 2013 he has managed the group risk function at RBS, reporting to CEO Ross McEwan.Stephen's appointment to the senior risk role at Westpac follows a global search by consultants at executive headhunter, Johnson.Westpac CEO Brian Hartzer described Stephen as an experienced banker and proven risk specialist."I am pleased to have someone of David's calibre join the group executive team," said the Westpac boss on Monday."He is a highly regarded global risk and financial services professional with over 30 years' experience leading risk teams in Australia, Asia, Europe and America, across retail, commercial and investment banking."Hartzer said Westpac's goal was to be one of the world's great service companies and that a culture of doing the right thing was critical to that ambition."David's track record in leading highly professional risk teams and embedding a strong risk culture across the banks he has worked in makes him an ideal fit for the Westpac Group."Stephen has also held senior roles at Deutsche Bank and Credit Suisse First Boston.