Coroner’s reports are not judged on their dramatic qualities. Yet Prime Minister’s Questions, the weekly political equivalent, is reviewed as if it were theatre.

Hardly anyone understands PMQs because, for most people, including those who sit on the benches in the Chamber, all they ever see is the performance in the Commons. The weekly tussle of of predictable questions & rehearsed answers, occasionally elevated by a terrible joke or a political skewering, often feels pointless.

In order to understand the real value of PMQs, one needs to have a seat inside the Cabinet Room on a Tuesday afternoon or Wednesday morning. Here on the long Cabinet Table, briefing documents from every department are coldly laid out like dead bodies on a slab in a mortuary. Each stack of papers contains the evidence of some government or political failure that might be raised in the Chamber. A skilled dissection begins: what happened? How did this thing on the table come to be here: was it accidental or is foul play suspected?

Inside No10, the team whose job it is to carry out these post-mortems is Research and Information. It is staffed with exceptionally adept civil servants and also with one or two Special Advisers, like me. I worked in R&I for Tony Blair and then Gordon Brown and prepared them for hundreds of PMQs. I have seen Whitehall bring out its dead and pile them up on that table.

There are three broad types of case.

The best and most common type of case is brought to us already prepared. Any decent departmental Private Secretary or Special Adviser will have taken the time to analyse the problem and deal with it before the Prime Minister sees it. Open and shut: simple.

The second type of case requires some work. Whitehall is territorial. Departments like to guard their patch. They are even more keen to disown other department’s problems. So, regularly, a problem is caught between two departments: neither is willing to own it and each blames the other. This is where No10 must step in. The PM or her Cabinet Secretary will insist that one of the departments must quickly take responsibility.

Third and finally, there is the worst type of case. There can be no orphans in Whitehall. Ministers cannot unparent their failures and leave them at No10. They cannot be permitted to let the Prime Minister take the blame. This will not be allowed to happen.

So every issue of any worth should be interrogated.

Wednesday mornings are ruthless. In before seven, the small PMQs team head one by one through the gates and up to the door. Later in the day, a custodian will watch and anticipate the arrival of anyone who comes close to the No10 door but at this hour the staffers earn the small privilege of knocking the door for themselves. There is a brass doorbell to the side but there are people still asleep in this house. Staffers know to lift the heavy black handle in the lion’s teeth and knock gently, just once.

Down the corridor, past the Cabinet Room: there is work to be done. On, into the rabbit warren.

The R&I team sit in a little over-crowded room, hemmed in by bombproof curtains, ugly metal filing cabinets and glass-fronted cabinets of old unread books. The clock on the wall, the telephone and the computer: they are all that matter. This is the pathologist’s den.

Five hours until Prime Minister’s Question Time starts.

Switch on the computer.

This is the expertise: scan hundreds of emails, find the problem. Look for the warning signs. They may not be obvious. Look for those symptoms submerged and disguised: the cryptically casual comment in a sub-clause from a Special Adviser, the ‘just-wanted-to-let-you-know-about-one-small-thing’ from a Principal Private Secretary, or the matter-of-fact group email from some cheery researcher in the Whips Office who is just doing what his boss tells him: all calculated to ensure the sender can later say truthfully that the Prime Minister had been informed of this problem before PMQs.

No10 knew. That’s what they want to be able to say. To slip out of the yoke of responsibility and dump it on the PM. No10 knew.

So they work in the expectation that it will slip under the radar. That no one in No10 cares enough about the rest of Whitehall to concern themselves with this little thing.

But if this is what you think will happen, you have miscalculated. Let me explain what is going to happen to you.

It all starts with Switch. The team who handle calls in and out of No10. There is no escaping Switch. They will get you anywhere.

You’re anxious. You probably didn’t sleep well. There is a wrinkle in your thoughts that you can’t uncrease. You just need this morning to go smoothly and then you can relax. It’s not long after 8.30. There is hardly anyone in yet. A quiet morning is all you need.

Keep your head down until PMQs is done. You put on your headphones and pretend to listen to the Today programme.

Your mobile rings. Number withheld. You let it ring out.

Your desk phone rings. Again: number withheld. Don’t answer.

The sanctimony on the radio is cloying. Now the phone rings on the desk next to you. You ignore it.

All three phones are ringing constantly and across the office the diary secretary is now looking at you quizzically. She waves at you. You point to your headphones and stare at your screen, with a frown that suggests you’re working on something important.

There is a tap on your shoulder and she stands beside you. You remove the headphone from one ear, ready to frown. She waggles her own mobile phone in your face. “It’s for you,” she says. “They said they know you’re here but if you’re in the bathroom, they’ll wait.”

You take the phone. A very polite woman, to whom you have never spoken before, addresses you by your first name. “It’s Switch here,” she says crisply. She is unfailingly polite. “PM’s office want to speak to you. Urgent. Putting you through now. Thank you.”

You see there is no escaping Switch. They will find you. You can’t hide. And once you take the call, you are trapped.

As soon as you are on that call, you are seeping information. Even if you say nothing, the fact that you said nothing is information.

Then they put you through to R&I. Here is what we tell you.

Look at the clock: in thirty minutes we will talk to the Prime Minister. Shall we tell her that there is a problem and that you are withholding the solution from her?

We are not interested in fault or blame. That is not our job. We do not threaten or show anger. All we require is information.

It is the Office of the Prime Minister that is asking you now. Not your boss. Whatever instruction you have been given, there is now permission from the highest authority for you to tell us what we need to know. You do not even need to think about this. It is the easiest thing in the world to release your grip on the information you hold.

Let me tell the Prime Minister that you were the first to share, not the one who refused to help.

Information flows to us, like water to the sea. Even if you don’t give it to us, it will find its way to us. It always comes here. It belongs to us.

Things sometimes just go wrong. People make perfectly understandable mistakes. This is not a prosecution: we are not judges. Tell us what you know. We’ll fix it. That’s what we’re here for.

There are some very good people with successful careers who have made a mistake along the way but what makes them very good is that they call us quickly to explain. We do not think any less of them for making a mistake. We admire them more for telling us what we need to know so quickly.

Just tell us.

But if you don’t. If you choose to dawdle, deceive or shift blame, then we will remember. We will add it to our repository of information.

Because we are the people who own information. We collect it. We distribute it. When the right time comes, then we will be unfailingly polite, remarkably helpful, and we will share whatever information is requested about you, just in the right way, at just the right moment. You may never even know we did it but we will fuck you up.

Because this is what we do. We know what information is, how it flows towards power. We know when to collect it and when to give it out.

So you will tell us everything.

This is how No10 interrogates the rest of Whitehall. This is how Government holds itself to account. This is the power and the purpose of PMQs.

Finally, an hour or so before noon on Wednesday, the work has been done. All the cases on the Cabinet Table have been dealt with. Problems solved. Responsibility assigned. Most will never see the light of the day. For the few remaining bodies, we use a few mortician’s tricks to powder them up and send them with the Prime Minister to the Commons.