Cameron Clyne, the departing chief executive of National Australia Bank, assumed the reins at the apogee of the global financial crisis, just six weeks before the collapse of Lehman Brothers.

His successor, Andrew Thorburn, walks into a vastly different job. In 2008 government backing for the banks was still implicit. Now the taxpayer safety net is explicit and the banks are much larger.

Their greatest risk, paradoxically, is the risk of reform.

The mere suggestion that the hegemony of the big four might be curtailed would send shockwaves through the sharemarket.

Greater competition is unlikely to happen soon but by the end of Thorburn's stewardship, the hegemony of NAB, Commonwealth Bank, Westpac and ANZ might be a bigger deal. So it is that NAB chairman Michael Chaney and his board have opted for an insider.

In step with the times, Thorburn is the quintessential ''good bloke'' selection.

The contrast with Clyne - also a ''good bloke'' appointment and also hailing from NAB's chief executive nursery, the Bank of New Zealand - is his banking experience. Formerly at St George and Commonwealth banks, he is a solid career banker of 27 years.

''Nice guy, family man, plays the drums,'' was how one friend described Thorburn on Thursday.

While the longer-term risks to the power of the banks are reform and technology, the chief risk at present is reputational rather than financial.

Ultimately, taxpayers carry the can for financial risk.

Thorburn has to run the tricky course between relaxing lending standards too far - knowing the state guarantees the business - and still not ceding market share to his rivals.

He is there to play a defensive game, to keep the stakeholders onside: government, shareholders and the community.

There is a spot of grumbling in the market that NAB ought to opt for an outsider, somebody who might offload NAB's lacklustre assets in the UK.

But an outsider would have meant higher risk at a higher price.

In any case, it's the wrong time in the cycle.

Why sell the UK when it is slowly turning around?

Chaney and Thorburn were talking no change in strategy on Thursday.

It seems the board has taken the opportunity to ''rebase'' salaries, though. In the new spirit of community, and spurning excess, pay has been falling.

Clyne was already lowest in the sector with a base of $2.7 million. When Ian Narev took over CBA he got $2.6 million. Westpac's Gail Kelly gets $3.1 million and Mike Smith at ANZ tops out at $3.3 million.

With bonuses those numbers double, but the new moderation sits well with community expectations.

A measure of the oligopoly that Thorburn and his peers are there to protect is that NAB, despite solid gains, has been constantly chided by analysts for being the worst performer of its peers since 2000.

It led the sector in 2013, however, generating a total shareholder return of 47.8 per cent against ANZ at 35.4 per cent, CBA at 31.8 per cent and Westpac at 31.9 per cent.

That, and a lift in market share, is belated vindication of sorts for Clyne's ''More Give, Less Take'' campaign.

The underlying strategy was to cut prices, win market share and then gradually reprice higher.

But the price-cutting cheesed off his peers no end, not to mention the sharemarket analysts. It only takes one player to upset a cosy oligopoly.

As CLSA analyst Brian Johnson put it: ''Stop cutting prices - NAB have a track record of strategically cutting prices to deal with any market share issues.

There can be a deep schism between the interests of shareholders and customers. Thorburn's challenge is bridging it.

@MichaelWestBiz mwest@fairfaxmedia.com.au