The fourth round of appearances by the CEOs of Australia's four major banks in front of the House of Representatives Standing Committee on Economics re-started yesterday.This was the first such hearing since the start of the royal commission into banking, and the politicians were clearly drawing on information and techniques that have emerged over the preceding six months.Commonwealth Bank was first to appear, with a first-time appearance by group chief executive officer Matt Comyn, alongside chief risk officer David Cohen, answering questions on a range of topics.Comyn offered a mea culpa in his opening statement: "As the royal commission has shown, there have unfortunately been failures of judgement, failures of process, failures of leadership, and in some instances, greed."We've been too slow to identify problems, too slow to fix underlying issues, and too slow to put things right for customers. We became complacent," he said.Comyn also acknowledge the "completely unacceptable" consequences of underinvestment in operational risk and compliance."The consequences were harsher the further down the organisation you went," he observed."Accountability has not been clear enough inside the Commonwealth Bank. To address this we have extended the government's new Banking Executive Accountability Regime across more than 90 executives."Cohen: "[CBA] has introduced a very thorough assessment of risk behaviours of senior execs. That has led to a much greater focus on risk by those decision-makers."Comyn noted that 15 CBA executives have so far appeared before the royal commission.In general discussion with the Tim Wilson, chair of the committee, Comyn said the royal commission had been a robust process, which drew mutterings from the observers.Comyn reminded the committee that in June CBA announced it would demerge its wealth and mortgage broking businesses into a separately listed entity to simplify the bank and allow each business to focus on its core activities and customers.That was followed this week by further announcements for customers in CBA's wealth business, including the rebating of grandfathered commissions to customers. Further changes are expected in the mortgage operations.House committee chair Tim Wilson also noted that as a result of the third investigation of the Big Four banks by this parliamentary committee, the ACCC was given an extra task - investigating the effects of the pricing of interest-only loans on the home lending market. That report is due on 19 November 2018.