The Prime Minister has spent his entire premiership hiding behind process – and yet it is process that has finally been his undoing.

This vote is not happening because the Opposition has invented a row, as desperate Labour MPs are claiming. It is happening because Keir Starmer appointed a known security risk and best friend of a convicted paedophile to our most important ambassadorial role. He did so despite risks being flagged and warnings made.

When the appointment blew up he had every opportunity to come clean, answer straightforward questions and level with Parliament. Instead, he misled Parliament by claiming due process was followed.

Month after month, he gave half-answers, ducked the point, and hoped that a mixture of jargon, delay and officialese would make the problem go away. It did not. Every evasion bred a new contradiction, every partial explanation raised new doubts, and every attempt to smother the story only made it bigger.

This is not a crisis manufactured by his opponents. It is a crisis caused by a Prime Minister who thought process could shield him from accountability, and who has now discovered that his own paper trail, the official evidence and the procedural facts have trapped him.

The real issue here is constitutional. Prime Minister’s Questions is not a game show. It is the one set-piece moment each week when the head of government is required to answer to the people’s representatives, the elected House of Commons.

When the Prime Minister is asked direct questions on a matter of national security and chooses not to be straight with the House – or does not even bother to answer the questions – it is, according to the rules, contempt for Parliament.

And when the answers he does give later unravel and his story changes, the issue is no longer simply bad judgment. It is a question of whether the Prime Minister has misled the House.

That is why a Privileges Committee inquiry matters. It is not some procedural sideshow. It exists precisely for moments such as this, when serious doubts arise about whether ministers have told Parliament the truth.

Labour MPs should stop pretending this is just another whipped vote and remember what they are there to do. They are not in the Commons simply to protect the Prime Minister from embarrassment. They are also there to uphold the integrity of Parliament itself.

What has made this worse is that the more Starmer has tried to shift responsibility on to officials, the less credible his own account has become.

Simon Case, who was Cabinet Secretary at the time, set out a process that required the necessary security clearances and due diligence to be acquired before the appointment of Peter Mandelson was confirmed. It presents us with direct proof against Starmer’s claim to Parliament that due process had been followed.

In addition, Starmer told Parliament there had been ‘no pressure whatsoever’ on the Foreign Office. Olly Robbins, the Foreign Office’s top official at the time, did not say that. He said there was ‘constant pressure’.

There is a reason this story will not die. Too much about it still does not add up.

Why did No 10 not simply level with the country when the first questions were asked? Why did it take leaks and committee evidence to drag out facts that should have been disclosed from the start? Why has every explanation raised new questions instead of settling them? And why, at every stage, has the Prime Minister’s instinct been to hide behind process, hide behind his officials, and hope that one more partial answer will get him through?

This is no longer just about Peter Mandelson. It is about whether the Prime Minister tells the truth when Parliament asks for it, whether he takes responsibility for his own decisions, and whether standards in public life still mean anything at all.

That is why Labour MPs now face a test of their own. They can circle the wagons, obey the Whips and tell themselves this is just politics. Or they can remember that they are Members of Parliament before they are members of the Labour Party.

They do not need to declare the Prime Minister guilty. They simply need to decide whether the questions that remain are serious enough to be properly examined. If they vote against that, they will be saying that accountability is for other people, not for them.

The country is watching. The people already suspect politics is full of half-truths, blame-shifting and carefully crafted evasions.

They look at this and see the same old racket: ministers saying one thing, officials saying another, and the truth emerging only in fragments. That is exactly why trust is collapsing and why protest parties thrive.

If Parliament does not get to the bottom of this properly, it will confirm the public’s worst suspicion, that there is one set of rules for the powerful and another for everyone else.