National Australia Bank directors have reduced Ken Henry's position on the bank's board to almost that of a figurehead chair after deciding to disengage him from the process of selecting the next chief executive of the company.When Henry announced his intention to resign his post on February 7, the controversial NAB chair was adamant he would stick around "for however long it takes" to find a replacement for outgoing CEO Andrew Thorburn."When senior people in the organisation say we understand, we are sorry, we are going to take accountability, we're going to, and in my case, I'm going to stay behind for however long it takes to appoint the right successor to outgoing CEO Andrew Thorburn," told the ABC's 7.30 Report."I'm going to stay behind to ensure appropriate board renewal, and that the board is strengthened by my departure, not weakened by my departure."However, the NAB board's attitude to Henry's involvement in the selection process appears to have undergone a shift in recent weeks as some shareholders publicly questioned the wisdom of him heavily influencing the appointment of the next CEO.In a filing to the ASX on Wednesday the NAB board revealed that it had established a selection process for the new CEO that will severely curtail input from Henry.A special selection committee chaired by non-executive director Ann Sherry will oversee the global search for Thorburn's replacement.While it will comprise other members from the board, NAB noted in the filing that the chairman would not sit on the committee.That means Henry will neither have a say in identifying candidates nor presenting a preferred shortlist for his board colleagues to mull over.Presumably, he will still be permitted to cast a vote when resolutions to appoint a new CEO are put to the board, but his ability to shape the outcome is likely to be limited to that function alone.Henry's determination to remain as chairman has perplexed some investors, who are questioning his purpose for staying now that his role in the CEO search will only be minor.A plausible explanation might be that the board has requested he do so because NAB's soon-to-be Acting CEO Phil Chronican might have put his hand up as a candidate to replace Thorburn permanently.Chronican's interest in the CEO position would come as no surprise to longstanding observers of the banking industry.Throughout his career Chronican has harboured a burning desire to lead one of the four major banks.A decade ago he was in the box seat at Westpac to succeed David Morgan but was steamrolled by Gail Kelly as part of the St George Bank acquisition.He also looked the most likely candidate to take over ANZ when he defected to the Melbourne-based bank in 2009 to join the executive team of former managing director Mike Smith.Chronican lucked out there as well.If he throws his hat in for the top executive post at NAB and misses again, the bank faces the risk of losing the director with the deepest banking experience on the board.Ostensibly, that is why the