Mark Duffy may wear the immaculate suits of a career banker – sober charcoal wool, a bright floral tie for flair – but beneath the pressed shirt is the dirtied bib of a man who has made a virtue of being a contrarian.

This was the man who last October infamously beat the drum for Bank of Scotland Ireland (BOSI) to be included in the Irish government's bank guarantee scheme only to spurn the eventual offer to join, claiming it would blunt the bank's "competitive edge" to fall under the ambit of the Department of Finance.

That competitive edge, which Duffy nurtured over his 17-year tenure as Bank of Scotland (Ireland) chief executive before leaving in April of this year, led to several signal successes for the institution, most notably the 2001 acquisition of ICC, the state-owned SME bank, and the 2004 launch of a new retail bank (later to take the Halifax brand).

But that competitive edge has also produced, to date, €1.3bn in writedowns on bad property loans, all of them written during Duffy's period at the top of the institution.

But Duffy isn't one to shrink from big challenges or major decisions. And he's copped on to his mistakes too, apologising last week for bad decisions he made while head of Bank of Scotland. He did not say whether one of them was aggravating the minister for finance. Of course, he was only able to stick his finger in Brian Lenihan's eye because the UK government had engineered a rescue for its own banks, including BOSI's new parent Lloyds, in the weeks following the Irish guarantee announcement.

Equal parts hard man and showman, Duffy kept a measure of attention on himself and his bank as he thrusted and feinted for advantage amid the chaos of crisis, boxing his adversaries sharply and then ducking away before they could strike back.

Now he's back in the mix with a privately-funded, Nama-style asset-management vehicle which he hopes will be able to buy portfolios of distressed debt from the five foreign-owned banks in the Irish market – including his alma mater as well as his old rivals, such as Ulster Bank.

Alongside him is property fund manager Kevin Warren, the yin to Duffy's yang, whose Warren Private Clients manages a €2.4bn property portfolio of its own. The division of labour, according to one industry source familiar with both directors, is likely to see Duffy as the entrepreneurial frontman, making the presentations, wooing the investors and the press, while Warren quietly gets down to the spade work of sifting out the most valuable nuggets from the boomtime sludge.

This dynamic was certainly in evidence at the Asset Resolution Corporation's (ARC) press launch last Tuesday, where Duffy clicked through Powerpoint slides and fielded questions, only bringing Warren into the discussion to address some of the more technical issues.

The relationship seemed perfectly amiable, but many in the financial industry are questioning whether it can last the 10 years or so it will take ARC to mature as an asset-management vehicle.

"There wouldn't be a clash of personalities so much as different strengths," said one source who knows both men personally. "Kevin would not begrudge Mark's front-of-house role, but there is a volatile history there with Mark. He loses it if something doesn't work out. A lot of driven people are like that."

Former colleagues of Duffy speak of him as a "true innovator" with a "good nose for a property deal", but also "a bit of a control freak who has little room for other opinions". The sense is that any source of friction would ultimately come from Duffy, that beneath his affable exterior is an operator determined to get his way. But amid that hostility that many seem to harbour for the man is a grudging admiration for a someone who has managed to come out mostly on top.

He had a rapid rise in banking, going quickly from ICC to venture capital firm 3i before landing an executive role at Anglo Irish Bank in 1987. By 1992 he was running Equity Bank, a low-key business lender which was bought by Bank of Scotland, where Duffy took the helm, reportedly pocketing a large personal pay-off in the process. He built BOSI up then by acquiring ICC and then putting Halifax on the map.

Crucially, unlike his rivals in the Irish domestic banks, Duffy wasn't pushed out of his last job – he left. As he tells it, he told the board of his intention to leave as early as spring 2008, but was asked to stay on to manage the transition once the crisis broke and Lloyds took over HBOS. Only then did the idea for ARC begin to take shape, he said, with a bit of prodding from Warren, who until the two got into business together was Duffy's wealth manager.

Now they have to make it work. This is where the rubber meets the road.

Financing from ARC's UK fund backers is key. Some reports have put the amount of money behind ARC at €3bn, but Duffy and Warren won't confirm this and industry analysts are sceptical the number is that large.

"I would be shocked if they had that kind of money. I'd put the figure at hundreds of millions at most," said one analyst. "Equity is easy to get but investors want to see a track record."

Yet one banker, a former senior colleague of Duffy's from his ICC days, spoke enthusiastically about ARC even while casting scorn on Duffy's "credit binge" at BOSI.

"It is a very easy solution that is going to leave Nama lying dead like a beached whale," he said. "They're getting in fast before anybody else and the foreign banks just want to get rid of everything and get out of Ireland. They're sick of the whole thing."

Duffy's rejection of Lenihan's offer of help last year may have been just a foreshadow of a developing tension within the ailing Irish banking sector.