In a patient, soothing voice, the chairman asked questions that were far more concerned with Supt Taylor’s own credibility than with the allegations he made which led to the establishment of the tribunal.

Supt Taylor has claimed that when he was head of the Garda Press Office in 2013-14 he conducted a smear campaign against Sgt Maurice McCabe following a direction from then Garda commissioner Martin Callinan. He also claims Mr Callinan’s then deputy Nóirín O’Sullivan was aware of the campaign. This is serious stuff.

Since he first made these allegations, Supt Taylor has also claimed that the force’s director of communications Andrew McLindon was also in the loop.

“I’ve been told that you and Andrew McLindon didn’t get on,” the chairman put it to Supt Taylor.

He disputed this, and said Mr McLindon was a likeable individual.

“I’m just wondering then why did you describe him in a text as a rodent?”

Supt Taylor said something about how Mr McLindon hadn’t told him that he was being transferred out of the press office when he was moved.

The exchange said much about the whole tenor of Supt Taylor’s evidence.

Repeatedly he was presented with documentation and the testimony of others that was completely in conflict with his position.

Nearly every time he replied with a version of “I don’t accept that,” or “Well, that’s not my evidence”. For somebody who has made the most serious of allegations, he provided no corroboration. That no reporter has come forward to say they were briefed by him is not a surprise. Anybody who would have been told by Supt Taylor that Sgt McCabe was a child abuser would most likely prefer to forget the briefing. To admit to receiving that kind of information might invite a host of other questions.

It is also highly plausible that Supt Taylor did, as he claims, actually spread lies about Sgt McCabe. According to the witness, Sgt McCabe was causing major headaches in Garda HQ. Mr Callinan had, in a Public Accounts Committee meeting in 2014, described the actions of Sgt McCabe in bringing forward his complaints about abuse of the penalty points system as “disgusting”. An internal Garda report into the matter was subsequently shown to have been highly deficient in identifying the abuses.

In such a milieu, Supt Taylor spreading lies in order to drag media focus away from Sgt McCabe’s complaints rings true.

However, he has given not one whit of evidence to back up his assertion that Mr Callinan ordered him to do so. Mr Callinan himself is the subject of a series of allegations that he spread lies about Sgt McCabe, describing the sergeant as a “kiddie fiddler” to different people. He denies this in each case.

Whatever about his credibility in that regard, he is on much firmer ground disputing Supt Taylor’s claims about him. The complete lack of any specifics by Supt Taylor has left the superintendent’s credibility in shreds.

His claims about Nóirín O’Sullivan must be viewed in an even harsher light.

Ms O’Sullivan transferred him out of the job he loved when she took over from Mr Callinan. Colleagues have said that Supt Taylor was “bitter” at the move.

Thereafter he continued, the tribunal heard, to act as a defacto press officer — leaking copious material to journalists in a completely unauthorised manner. It was repeatedly put to him that he was “fixated” with Ms O’Sullivan and that this was behind naming her in his protected disclosure. Once again, he denied this.

There is no evidence whatsoever that Ms O’Sullivan knew anything about a smear campaign or briefed anybody negatively about Sgt McCabe. In terms of contributing to the judge’s task of finding out what, if anything went on, the man at the centre of it all could hardly have been of less assistance.

Later, it was back to the future when Alan Shatter stepped up to give evidence about how he had encountered Ms D, the woman at the centre of a discredited allegation against Sgt McCabe.

The former minister for justice told the tribunal that he was in a bad place in June 2014 after his resignation from office weeks earlier when Paul Williams rang him and asked him to meet Ms D, the woman who had made the historical allegation against Sgt McCabe in 2006.

They met in the Merrion Hotel. This was 16 years after she had alleged the incident had occurred, the nature of which wasn’t even criminal. It was eight years after the matter was investigated and effectively dismissed by the DPP and local state solicitor.

“She was very stressed,” Mr Shatter told the tribunal. “I found her stress distressing. I suppose I was somewhat stressed at the time myself.” Shatter listened to her and decided to bring up her concerns in the Dáil that the allegation had not been properly investigated in 2006. He didn’t want to bring the matter to the Taoiseach lest it be “perceived as trying to exact some revenge on Sergeant McCabe”. So he just brought it up in a debate.

“I did it discreetly so I wouldn’t ignite another frenzy and bring the hounds of hell down on me again,” he said.

Martin Callinan is to appear before the tribunal today.