After a half-year of nationalisations, botched recapitalisations, managerial departures and arguably the biggest destruction of shareholder value in the history of Irish business, surely the past six months have been the most tumultuous period ever in Irish corporate life?

Well, not really, because the period of greatest tumult, when rumour and fact were the most difficult to disentangle, was arguably the period immediately before and after March 2008.

During this time Irish bankers were a less humble species than they are today. Criticism of their business models and their bad loan provisioning was only beginning to enter the public domain, and even those making mild-mannered complaints were dismissed as either national economic saboteurs or outsiders with no real feeling for the unique nature of Irish banking.

I remember a conversation with a senior member of Anglo Irish who was incensed with an equity analyst who had, rather meekly, raised some low-level concerns in March over the bank's exposure to commercial property lending. The Anglo executive's description of the analyst cannot be repeated in a family newspaper, but let's just say it involved the analyst doing something anatomically impossible and very painful to himself.

The frenetic atmosphere of last March was caused in the main by the movement of financial tectonic plates on Wall Street, with Bear Stearns gobbled up by JP Morgan Chase. Ultimately Bear Stearns was taken out after the wholesale markets, and repo lenders in particular, lost confidence in the US bank.

This lack of confidence soon stretched across the Atlantic, and on 17 March, Anglo Irish Bank stock dropped 23% during an alarming sell-off. Anglo came into that trading day at approximately €6.90 a share, a far cry from the 22 cent at which it was eventually nationalised this year.

The bank's executives were indignant, at least in private, at the treatment meted out to the stock on St Patrick's Day, believing the market was making a ludicrous connection between it and Bear Stearns, a bank with a huge subprime exposure. Anglo vehemently disagreed with the stock price fall and blamed a murky group of London hedge funds for the decline.

These hedge funds, and a coterie of brokers in Dublin, had spread malicious rumours about Anglo, the bank complained. It passed these reports onto the Financial Regulator. The reports were never substantiated in public by Anglo, although it did engage in some angry correspondence with some Dublin brokerages.

Anglo has not pursued any court actions in Ireland over the reports of rumour-mongering. It did take a legal action in London last summer over an email it claims was sent suggesting Merrill Lynch had withdrawn a $2bn credit line from the bank during the March frenzy.

Anglo Irish filed a complaint in the London High Court claiming that an employee of London stockbroking firm Mirabaud Securities sent an e-mail on 29 February that said: "Anglo-Irish, ML pull a $2bln credit line? Rumour." The Irish bank said last week it was no longer pursuing any actions against this stockbroking firm.

On 20 March last year the Financial Regulator, in conjunction with the FSA in the UK, without naming Anglo, said it was examining unusual trading patterns in Irish shares. It said it was concerned that certain "false and misleading" rumours were linked to these trading patterns.

Media reports subsequently suggested Irish brokers had to provide records of transactions; the Sunday Tribune has talked to stockbrokers who claim they had to hand over email records and some phone evidence as part of the investigation.

But since then, nothing has been heard of the regulator's work. The regulator has not publicly sanctioned a single broker or market participant despite its 20 March statement threatening to "actively pursue" anyone spreading false rumours.

The regulator has not even been prepared to say whether the investigation has concluded or not, or to explain why it has not been possible to sanction anyone for such activity.

A lack of evidence is clearly one possible explanation. Finding a direct link between a market rumour and a specific trade is a tough ask for any regulator, particularly one with as little experience of such investigations as the Irish regulator, led at the time by Patrick Neary.

But equally, a critical problem the regulator may have run into is that Anglo's 'Saint Patrick's Day massacre', in hindsight, may have been the result of rational market actions, rather than a selling frenzy fuelled by poisonous rumours.

The Sunday Tribune has seen internal Anglo memos outlining what was actually happening in March 2008 and it is not a pretty picture. In fact, if market participants had been privy to the extraordinarily stressed position of Anglo at that time, it could be argued that the sell-off would have been even more pronounced.

For example, the material seen by this newspaper shows that Anglo suffered "significant customer deposit outflows" in March. In this case, Anglo claims the outflows were caused by the misleading market rumours, not the other way around.

This is a curious assertion, because the bank's own records suggest that, on 8 March, Anglo received a deposit of €750m from a division of Irish Life & Permanent. Anglo's own records about this state: "This had the effect of enhancing customer deposits. As a reciprocal arrangement, the bank placed a greater amount of cash with Permanent TSB, the banking entity".

In other words, Anglo appears to be admitting in internal memos that before the 17 March 'massacre', there was a pressing need for customer deposits to be bolstered.

Rumours of the bank's weakened balance sheet, if they circulated in rumour form, would not have been too wide of the mark, based on this reading of events.

Worries over customer deposit withdrawals lingered on into the summer with State Street, Delta Lloyd and AIB Investment Managers making withdrawals in July and August.

If one takes the Anglo internal memos at face value, the bank had serious and potentially dangerous customer deposit problems in early March. But by 20 March the Financial Regular – at least publicly – was chasing down a different problem, of hedge funds who were spreading rumours about the liquidity of Anglo Irish bank.

What we don't know is whether or not it is conceivable that, small details aside, the rumours circulating at that time were actually reasonably close to what was actually happening.

If that is the case, the Financial Regulator's investigation was a waste of time and resources when there were bigger issues out there to be tackled. It may also explain why no company or individual has yet been prosecuted or sanctioned as part of the regulator's "misleading rumours" market abuse investigation.