South African private bank Investec saw full year profit tumble 22% following a sharp decline at its investment banking and private banking businesses.Operating profit before tax for the year ended 31 March 2009 fell to £396.8m from £508.7m a year ago, but slumped by 61% at the investment banking unit to £28.2m.The company made just £80.5m from private banking, down 51.6%, on the year before, while a drop in private client activities had profits there down 46% to £104.6m. Profit fell 13% at the asset management division to £66.2m. But capital markets proved a bright spot, raising profit by 22% to £141.4m, helping overall group operating profit, excluding impairment losses on loans and advances, rise 4.8% to £652.9m.Investec said it recorded operating profits across all divisions and geographies, underpinned by a "solid" recurring revenue base.'We believe this is a creditable performance given the very difficult operating conditions we faced," said chief executive Stephen Koseff.