At the heart of the Mandelson saga is one colossal political misjudgement – the appointment of Peter Mandelson to the role, despite everything already known about him. Nobody now disputes this.

The fault wasn’t in the vetting system but in the decision to announce Peter Mandelson before vetting him

It has also become clear, not least from the evidence to the Foreign Affairs Committee from Olly Robbins and Philip Barton, successive heads of the Foreign Office, that the appointment was not done by the book. The right order in appointing someone to our most senior Ambassadorship is this: do the vetting first, then get the approval of the King, then the formal approval of the US government, and only then announce it. Ideally, you might even speak to the head of the Foreign Office – the Ambassador’s line manager – before you make your decision. Everyone now knows that this was not the order in which things were done.

Instead of doing things by the book, the book was thrown at the head of Sir Olly. As a result, one of the most talented, committed and decent public servants of this generation has – at least for now – been lost to public service. Britain will not be safer or better off for his firing.

In an effort to find others to blame, damage has been done to our constitution, in small but subtle ways. Because a Permanent Secretary was summarily dismissed for doing his job, every civil servant will now be more cautious about deciding anything without reference to Ministers, in case it gets them fired. The state will have become less nimble.

And more damage is on the way, thanks to the review set up last week into the vetting system. This was a classic case of ministers wanting action to show grip in a crisis. Something bad has happened and so something must be done. The vetting process has clearly failed, and therefore we must have a review.

I am sure Sir Adrian Fulford will do a very good review. As a former Lord Justice of Appeal and Investigatory Powers Commissioner, you would hope so. He has been given a clear steer by the Prime Minister – something has gone badly wrong in the vetting process, and must be fixed; ministers weren’t told things they should have been told, and this must never happen again; departments overruled the United Kingdom Security Vetting (UKSV) decision, and this was wrong.

Each of these premises is false. The fault was not in the vetting system, but in the decision to announce Mandelson before vetting him. Everything else that went wrong cascaded from that.

The Prime Minister fired Robbins for not showing him a document that Robbins himself had not seen, and should not have seen. The idea that ministers should start to see inside the vetting process is a truly awful one. As someone who has been through it multiple times, I know how intrusive it is (and needs to be). The whole process can only work if those involved know that ministers will only ever learn the outcome.

The Foreign Office ‘overruling’ UKSV was not a bug but a feature. The current system is sensible: UKSV staff identify the risks; the department’s specialist security staff, who understand the complexities of diplomatic life abroad, work out if that risk can be mitigated. We now know that on the very page of the UKSV review that supposedly ‘failed’ Mandelson, UKSV described Mandelson as “a very borderline case” and quite properly referred it to the Foreign Office for a decision. This was the system working as it was designed to work.

So the entire review is founded on a series of false premises, and risks making a good system worse.

Ministers have already started this process. When the storm about Mandelson’s vetting broke, Chief Secretary to the Prime Minister Darren Jones went on Good Morning Britain and said: ‘As soon as I found out last night… I suspended the rights of the Foreign Office to overrule security vetting recommendations.’

Since then, ministers have made clear that the Foreign Office no longer has the final say on Developed Vetting clearance if UKSV recommends a denial. They have also introduced Mandatory Ministerial Briefing, so if UKSV identifies red flags or recommends denial, a due diligence summary must be provided to the appointing Minister before any further action is taken.

Both these steps will make the system worse, not better. They will make it less pragmatic, less able to balance risk with mitigation, and even less comfortable for those involved, knowing that Ministers might end up poring over their most personal secrets in a ‘due diligence summary’.

The Fulford report will no doubt come up with many fine recommendations, each of which will make sense on their own merits.

But Sir Adrian has been set the task of preventing a set of things from happening again that either didn’t actually happen in the first place, or were the system working as designed. What the review should say to ministers is this: ‘Actually, the system is working pretty well, as long as you don’t keep naming people with known issues to sensitive ambassadorial appointments before doing the vetting’.

Instead, it will give ministers a moment to stand up in Parliament (or sit down on Good Morning Britain), and announce a series of actions. And ministers love announcing actions, particularly in response to things going wrong, and most of all to distract attention away from bad decisions that they themselves have made.

The most dangerous eleven words in the English language are these

At the end of it, the system will not work better; the relationship between ministers and civil servants will not function more effectively; and the country will not be safer. And the review won’t even do the real job that ministers wanted from it, as no one will be persuaded that the issue with Lord Mandelson’s appointment was one of officials overseeing the vetting process rather than the PM’s decision to appoint him in the first place.

The most dangerous eleven words in the English language are these: ‘And that is why I can announce to the House today’. The sad truth is that you cannot legislate against bad decisions, you cannot reduce every risk dial to zero, and awful things will always happen. The real risk in trying to stop them ever happening is that over time we accumulate so many rules, restrictions, safeguards and processes is that we simultaneously infantilise the debate and paralyse the country.

I hope that one day a minister would stand at the Despatch Box and say: ‘This terrible thing has happened, because we intentionally took some risks and we were unlucky. In response to this terrible thing, I propose to impose no more restrictions or safeguards than already exist, because I judge the current balance to be appropriate, even in the light of this terrible thing.’

I see no chance of that happening any time soon. So we will carry on tying the country in knots, until there is nothing left in the country but processes, safeguards and rules.