Summer's over, the tribunals are back. When will we be rid of these turbulent priests of Dublin Castle?

In quiet moments, when hanging his baskets, Bertie Ahern might ask himself just that question. Tomorrow, he will finally be asked a question that he has been gagging to answer since his slow decline and fall began a year ago to the week. Did you ever receive a bribe from Owen O'Callaghan?

Ahern is back in the witness box, scheduled for two days of evidence. Nothing is ever certain about the evidence Ahern gives under oath, but he can be reasonably confident of one thing ahead of this stint: it will be a hell of a lot easier than what he has had to endure so far.

Unless another dark recess of his financial catacombs has been discovered over the summer, there will be no further excavation of all the money that poured into his accounts. He is off the hook. For now.

Instead, the inquiry will focus on the flip side of the allegation. As many of you may not recall, Ahern's woes began with an allegation by developer Tom Gilmartin that the then minister for finance received a bribe of £80,000 from O'Callaghan. Both men deny that any money passed between them.

Gilmartin and O'Callaghan were jointly developing Quarryvale in the early 1990s. The development became Liffey Valley shopping centre. A rival development, the Blanchardstown Centre, was seeking tax designation, which would have been a major boost to its business, and a blow to Quarryvale.

Gilmartin claims that O'Callaghan told him that Ahern had been bunged 80 big ones to ensure that Blanchardstown didn't get the tax designation leg-up. The two developers subsequently fell out and O'Callaghan developed Quarryvale alone.

Gilmartin is bitter about how he was treated by O'Callaghan, the banks and the political establishment. He has provided serious fodder to the planning inquiry. His evidence has shown how the country was run, the manner in which players such as George Redmond, Liam Lawlor and Padraig Flynn used their public positions to enrich themselves. He has also been central to the exposure of the corruption which was the engine behind planning in Dublin at the time.

Much of what Gilmartin alleged has stood up to scrutiny. Some of what he has alleged appears far-fetched. The three judges of the tribunal will ultimately have to sift through the chaff to locate the wheat of his evidence.

Poor Bertie was dragged into the centre of this morass by Gilmartin's allegation. Over the last couple of years, Ahern has repeatedly claimed that he is the victim of a spat between two wealthy developers.

On one level, he may be entirely correct. His problem is that when the inquiry attempted to follow the alleged bribe through his bank accounts, they came up with all those pots of sterling, which were explained away by Ahern with a bizarre, unlikely and ever-changing story. This culminated with his evidence that some of the sterling was the proceeds of bets won on horses in the UK.

Ultimately, so far, absolutely no evidence has been uncovered to suggest Ahern received a bribe from O'Callaghan. A whole slew of circumstantial evidence uncovered suggests that he may well have received an awful lot of money from an unidentified person or persons.

Tomorrow, the flip side of the allegation against Ahern will be explored. Did the then minister for finance act in any way favourable to O'Callaghan that might be construed as motivated by the receipt of a bribe?

The tax designation arose out of an urban renewal scheme launched by the government in 1994, designed to boost commerce. It involved tax incentives for retail tenants, thus attracting business to designated centres.

Ahern will be questioned on his contacts with O'Callaghan and the principal of the company behind Blanchardstown, John Corcoran, in the mid-1990s. Ahern says he has no recollection of ever discussing tax designation with either man.

There is documentary evidence that the Department of Finance was against tax designation for Blanchardstown, as it was already up and running by mid-1994. This would imply that O'Callaghan had nothing to fear on that front.

The tribunal also has possession of bank documents which suggest that O'Callaghan was confident that Blanchardstown would not receive designation. What exactly might have fed his confidence will be of interest to the inquiry.

For Ahern, this is all bread-and-butter stuff. There is unlikely to be a smoking gun under the mountain of faulty memories, departmental and bank documents and his explanation of the politics of the day.

The only real discomfort Ahern could face will be under cross examination by Gilmartin's counsel. In 2004, during an earlier module, the then taoiseach was subjected to a torrid time by Gilmartin's lawyer, Hugh O'Neill.

So Ahern's credibility is unlikely to suffer a similar drop to those he has endured after all his recent appearances at the inquiry. His main worry now is what the three judges will determine about his personal finances when they issue their report.

On a wider front, the unravelling of Quarryvale continues apace. Most people are bored by the details. Some question why an expensive inquiry is still bothering with it.

Yet it remains the most important aspect of the decade-old inquiry. It involved planning decisions that affected a large tract of west Dublin which has been beset by social and economic problems.

Instead of the building of a town centre designed to regenerate north Clondalkin, a shopping complex targeting commuter traffic was constructed. The evidence so far suggests that there was extensive bribery involved. Developers and politicians conspired to undermine the planning laws by suiting their own interests rather than "the common good", which has primacy in law. The truth about that sordid episode deserves to be fully told.