Michael Buckley may have served just four years as head of Ireland's largest bank, but in that short period he has survived challenges most chief executives never face in a lifetime.

Twice within a two-year period, Buckley felt compelled to tender his resignation, an offer that was twice refused.

Described as a corporate "Houdini", he faced his greatest challenge just nine months after his ascent to the top job when a phone call from Baltimore, Maryland, US, revealed that the bank's former star currency trader, John Rusnak, had lost $691 million (€554 million) in fraudulently trading the bank's money.

While serious failings in AIB's internal compliance and communications systems were found to have allowed the fraud, many see Buckley's handling of the crisis as perhaps the greatest achievement of his tenure at AIB.

Assembling a small team, the former stockbroker steered the bank through the uncertain period that followed, limiting the damage to AIB's brand and share price and focusing most of the blame in Baltimore.

Having weathered the storm, the bank was hit with another crisis just two years later when AIB was found to have overcharged customers over an eight-year period. The scandal, which also saw overcharging practices unearthed in other areas of the business, cost AIB some €50 million.

AIB's reputation was further tarnished when it emerged that a number of its most senior former executives were among the beneficiaries of Faldor Ltd, an offshore investment group being investigated for breaches of tax law.

While some believe Buckley was simply unlucky, getting landed with the fallout from problems not of his making, the crises overshadowed his period as head of AIB.

"He presided during a period when the bank didn't exactly cover itself in glory," one fund manager said yesterday.

"Chequered" is how a banking analyst described the Corkman's career at the top of AIB, adding it had been tainted by the various scandals and revelations.

On the plus side, market observers note that Mr Buckley, who first studied for the priesthood before opting for a career in the civil service, leaves the bank in good shape.

His decision to merge US subsidiary, Allfirst, with M&T, in exchange for a stake in the enlarged group in the wake of the Rusnak scandal is seen as a good one.

Meanwhile, the rest of the bank's business remains robust. With record pretax profits of €1.4 billion last year while and the share price at six-year highs, investors are likely to have few complaints.