APRA chair John Laker shot down a possible topic for lively debate yesterday that may be addressed by the forthcoming financial system inquiry.Laker, who was giving the Warren Hogan Memorial Lecture at the University of Sydney, touched on a topic of interest to the late economist and Westpac board member."The notion of 'narrow banking' is still with us," Laker said, even if "not in the pure sense advocated by Hogan and others, but in the form of proposals — associated with the names of Volcker, Vickers and Liikanen — for the structural separation of retail banking from proprietary trading and other high-risk activities.""[This is] a complicated issue, but not one for Australia," he said.And a topic too complicated for him to offer a rationale for despite giving the lecture it seems.