This is the week when Scottish First Minister Nicola Sturgeon’s evidence to a Holyrood committee may mark her downfall. If she is found to have breached the ministerial code of conduct in the Salmond-Sturgeon slugfest she will be expected to resign.

But, this is Scotland, where the competence of juries is questioned freely by First Ministers. Even if the jury of a Holyrood committee finds a breach has occurred Sturgeon is likely to cling on. She gives every sign of considering herself a higher court, her own judge and jury.

She may stay. Others, Leslie Evans, head of the Scottish Civil Service and Lord Wolffe, the Lord Advocate in charge of the Crown Office, will likely be thrown under the bus. Peter “Alex pops round all the time” Murrell, Chief Executive of the SNP and Sturgeon’s husband, will be tossed out of party HQ, if not the family home.

For those new to this long-running 21st century Scottish Play, the complex background is explained in excellent Reaction contributions by; Gerald Warner here, Maggie Pagano here and Olivia Gavoyannis here. All you need to know to bring you up to speed.

I want to focus on one critical aspect of the miserable saga. Six years of Sturgeon primacy have destroyed the doctrine of separation of powers in Scotland. The Executive, the SNP dominated legislature and the compliant Crown Office now all dance to the tune of the First Minister. Nicola Sturgeon has achieved the seemingly impossible. She has created a nation that, should it ever gain independence, no longer qualifies to join the European Union. Scotland fails the EU’s primary membership test, at the first hurdle.

The primary requirement of any applicant for EU membership is to have stable institutions, guaranteeing “the rule of law”. Former First Minister, Alex Salmond, is well aware of that. Hence his acerbic and devastating point during evidence to the Holyrood Committee last week, that future aspirations to independence “must be accompanied by institutions whose leadership is strong and robust, and capable of protecting each and every citizen from arbitrary authority.” As matters stand, the goal of Scottish independence is on hold. No IndyRef2.

In Salmond’s damning judgement, the EU’s strong and robust standard no longer applies in Holyrood. His thunderclap is all the more deafening as it comes from a man whose whole life has been dedicated to the cause of independence.

Astutely, he added the caveat that Scottish institutions were not to blame, only those who lead them. So, in his opinion the rot is reversible if the canker at the top of government is pruned. Not difficult to spot who he means; Nicola Sturgeon, First Minister, Leslie Evans and the Lord Advocate.

But the dark matter of redacted evidence – to which Salmond could not refer in his four hours of testimony last week, as to do so could make him liable to prosecution for contempt of court – exerts an unseen force that makes a cop out likely. Without all the facts in plain view it is likely that buckets of “he said”, “she said” whitewash will be slapped on this epic battle between the former and current leaders of the SNP. Sturgeon hopes the public will become bored with the complexity and “move on”.

It need not be so. There is a means of achieving necessary clarity prior to Sturgeon giving evidence on Wednesday. It is the use of parliamentary privilege, either in the Holyrood Parliament or the House of Commons.

Tantalising documents concerning the critical meeting between Geoff Aberdein, Alex Salmond’s aide, and Sturgeon on 29 March 2018 – the meeting that she “forgot” – are held by Salmond’s solicitors. He said so. He could not have waved a more visible flag if he’d tried. “Come and get it!” Other documents with redactions – which may or may not be relevant – are also available in full.

If all were in the hands of a backbench MP in Holyrood or Westminster with a righteous interest in full disclosure, the material could be read into the record under parliamentary privilege. All would be, at last, in the public domain. Crucially, that would allow proper cross-examination of Ms. Sturgeon on matters she seems determined to evade.

The doctrine of parliamentary privilege was tainted by the 2010 MP’s expenses scandal, when it was invoked – hopelessly wrongly as it turned out – to protect MPs from their own skulduggery. That argument quickly came a cropper, but the attempted corruption of the principle had to be quickly put right. There followed the Parliamentary Privilege Report presented to Parliament by the Leader of the House of Commons and the Lord Privy Seal in April 2012.

That 2012 report was a restatement in modern terminology of well-established doctrine dating back to Magna Carta, first codified in the 17th century after the “Glorious Revolution”. To put it simply, after William of Orange and Mary were invited to ascend the throne, from which James II had been unceremoniously chased, two acts of parliament were passed, one in Westminster, the other in Edinburgh, to curb the natural tendency of the Crown to cow the legislature. In other words, guarantee the separation of powers and free speech in both parliaments.

The right of a Member of Parliament to immunity from prosecution is neatly put in a rejoinder from the Commons to James VI in 1610: “That every Member of the House of Commons hath and of right ought to have freedom of speech … and … like freedom from all impeachment, imprisonment and molestation (other than by censure of the House itself) for or concerning any speaking, reasoning or declaring of any matter or matters touching the Parliament or parliament business.”

If the Salmond-Sturgeon affair is not resolved in the full light of all available facts it will drag on, questions unanswered, a permanent stain on Holyrood’s reputation. Wanted: a principled MP or Peer at Westminster to step up, make use of the privileges to which they are historically entitled and provide clarity in the national interest.