Public inquiries are strange creatures. It is easy to see why governments, particularly the one in Edinburgh, hate them and will do their best to avoid them.

Mainly for the same reasons, it’s also fair to argue that they are vital and have a way of revealing truths that no other process gets close to. One form of compromise, I suppose, is to demand them sparingly. Another might be to design a credible alternative which addresses the genuine downsides: that they take for ever and cost a lot.

This week, we have been spoiled for choice in Scotland thanks to two inquiries set up by the UK Government. The Covid Inquiry has secured most of the headlines and the evidence confirms the strengths of the public inquiry mechanism.

If it had been left to any lower form of investigation, the truth about Nicola Sturgeon’s WhatsApps, Jason Leitch’s bedside rituals and much else would have remained buried until all risk to reputations had disappeared into the sands of time.

Whereas a Parliamentary committee can be danced around and obstructed without any real redress available, that is a lot harder with a judge-led inquiry where evidence is given under oath. Failure of disclosure or destruction of evidence are potential criminal offences.

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In that setting, truth stands a chance against a glib tongue. Questioning by a well-briefed KC is in a completely different league from the honest efforts of politicians who are only allowed to ask a few questions and almost certainly lack the forensic skills.

While there was plenty of interest in the Scottish end of the Covid probe, I opted for watching a live stream from London where evidence of particularly Scottish interest was being taken by the Post Office Horizon inquiry. It proved compulsive viewing.

Here again was information and context which would not have been brought to light within any other format. The inquiry selected two case studies involving investigations conducted from Scotland though one of them was in Newcastle; the other in North Uist.

Over two days, evidence has been led from the two Post Office investigators who handled the case of William Quarm, the sub-postmaster at Paible in North Uist, whose is one of only two wrongful convictions in Scotland to have been fully overturned by the Court of Appeal.

The process by which these charges were brought has already been subjected to much doubt and some belated apologies. But this was evidence from the front-line: two individuals who had no qualifications in criminal investigation, no training worthy of the name, minimal knowledge of Scots law and financial incentives to meet targets which the Post Office kept raising.

If it is still possible to be shocked by this affair, then these two days of evidence crossed that threshold - and the procurator fiscal who decided to prosecute on the most threadbare evidence, now discredited, will be heard from today. The case for an inquiry into the Crown Office and Procurator Fiscal Service’s role is itself strong, though I had better stop short of demanding a “public inquiry”.

The Herald: Jason Leitch after giving evidence to the Covid Inquiry on Tuesday Jason Leitch after giving evidence to the Covid Inquiry on Tuesday (Image: PA)

The courtroom style of questioning has the advantage of producing theatrical moments and we came close when a former Perth-based investigator, Raymond Grant, was being cross-examined. Mr Grant did not trouble to conceal his contempt for the inquiry and was only there at all because Sheriff’s Officers turned up at his door to serve a writ on him for ignoring the summons and the inquiry’s request for a witness statement.

Mr Grant testified (under oath) to having been completely unaware of problems with Horizon when pursuing the North Uist case and others. Pressed repeatedly by Jason Beer, the lead counsel, he maintained: “I was not aware of any operational difficulties with Horizon." Then the legal dagger went in as a memo written in 2002 by Mr Grant went up on the screen.

At that early stage, he complained to a superior that the Horizon Help Line had been telling sub-postmasters that Horizon was faulty and inaccurate. But Mr Grant’s problem was not that it was “faulty and inaccurate”. It was that the Help Line was telling people - thereby “questioning the integrity of Horizon”.

It was a despicable performance capped by him repeating the false allegation that Mr Quarm was guilty - a man who is long dead and in no position to defend himself and downright wicked in terms of Mr Quarm’s family who finally cleared his name after more than a decade of purgatory. To repeat the allegation without adding a shred of evidence was sheer cruelty from a man who opened by stressing his Christian credentials.

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A wider truth that emerged from these exchanges was that the people entrusted by the Post Office to pursue Horizon cases had absolutely no professional, technical or ethical qualifications for doing so. It was utter madness at every level and the longer it went on, the more unforgivable it became to plough on with cases which so many people knew to be deeply flawed.

The Horizon inquiry has been going on since June 2021 and is already booked up well into next year. That is the downside. But if it had never been set up, we would not now be getting access to evidence which has acquired a far wider audience in recent weeks.

In Scotland, public inquiry timescales have been given a bad name by the Edinburgh trams (nine years) and Skeku Bayoh (five years and counting). However, there will be something far wrong if we can never have the highest levels of interrogation and disclosure on the grounds that the inquireis might go on for ever. Is that a genuine objection into scandals like, for example, the Ferguson ferries debacle or merely a convenient excuse? Are time-limited inquiries conducted to the same judicial standards impossible to design?

After what I have heard and read over the past couple of days, I would very much like that possibility to be explored. They have been more educational about Scottish realities than a year in Holyrood.

Brian Wilson is a former Labour Party MP and Energy Minister