Investec Bank (Australia) has confirmed reports that its chief executive of four years, David Clarke, has resigned. Investec's chairman, David Gonski, said in a statement on Friday that Clarke had agreed to stay on for six months while a successor is found.The timing of Clarke's departure is strange. In 2010, in the wake of the financial crisis, he initiated a four-year restructure of the bank. This doesn't appear to have been completed.When Clarke took the top job at Investec, in 2009, he started moving the business away from its base in property finance. He set out to diversify the business and move its revenue base from interest to non-interest income.He devised an ambitious restructuring agenda, which included moves into corporate advisory, capital markets and securities. The area where the plan has had most impact has been in the expansion of the bank's resource finance and asset finance businesses, and in the growth of its professional and private client banking activities.In July last year, Investec doubled the size of its asset finance business when it bought Alliance Equipment Finance - a vendor finance specialist whose relationships include Konica Minolta and Cisco. It got into the asset management business with a $50 million fund-raising for the Investec Global Aircraft Fund.In its professional and retail banking division, it expanded its product range with the launch of an innovative notice period account in 2011. It also launched Visa Signature and Visa Platinum credit cards.But, despite all this activity, earnings growth has been slow. In the year to March 2011, it made a pre-tax profit of A$2.1 million and in the year to March last year it made a loss of $71.6 million.Last year's loss was related to the run-off of the property development loan book, which has largely been completed now. However, profit from the bank's core activities fell from $51 million, in 2010/11, to $25.1 million, in 2011/12 - a result of costs associated with the restructure.The bank's 2012/13 results should be out next month. They will give a clearer picture of what sort of legacy Clarke will leave behind at Investec.