Today’s coverage about Andy Coulson’s vetting prompts me to write a little blog about what developed vetting is, and why people have to go through it.

When I started my job as Head of Communications at the Treasury in 2003, every induction conversation ended up with me being asked: ‘Have you been DV’d yet?’ ‘Not yet.’ ‘You’ve got to get that done.’ I soon found out why. Briefing sessions with the Chancellor ahead of international summits would be broken up as Gordon’s PPS, Mark Bowman, said: ‘Damian, you need to go out for a bit.’

This was especially frustrating for my colleagues if this happened in confined spaces, such as the Royal Flight en route to Brussels, where I couldn’t ‘go out for a bit’, much as Gordon seemed to wish I could. It would have been impossible – and I mean impossible – to do the job I later did in 10 Downing Street if I’d been obliged to keep getting up and leaving the room every time something ‘top secret’ was discussed.

But at the Treasury, I was a bit baffled by the fuss. I’d been privy to Budget secrets for years, and – at Customs – I’d been present at planning sessions for major anti drug-smuggling operations. Why did I need DV clearance now?There are two reasons:

(i) nothing quite prepares you for the eye-watering ‘wow!’ factor of some of the things you hear after you’ve been DV’d – they are Top Secret for a reason; and

(ii) if you’re put into a high-profile role, you automatically become a person of interest for foreign security agencies, terrorist organisations, etc., who may want to target you with honey-traps, financial blackmail, email hacking, or anything else. So if your vulnerability to those attacks hasn’t been thoroughly checked out, you remain the potential loose brick in the wall.

So after a few weeks in the job, my time came. First I had to fill in an enormous form – think a mortgage, passport and adoption application all-in-one – requesting everything from bank account details to your grandmother’s maiden name. Why grandparents? So they can do background checks on your full extended family, and avoid the headline: “Olympic Security Chief Is Saddam’s Cousin.”

I had to supply a handful of potential referees, at least one of which would be interviewed either before or after my interview to check compatibility with my answers. And I was then asked who I wanted to do my interview: the choice was described as ‘A kindly spinster aunt-type who wishes you’d settle down and get married, or a retired sergeant-major type who thinks you’re a poof.’ I went for the spinster aunt.

When we sat down together, she looked over her half-rim glasses and said these chilling words: “Now I’ve done hundreds of these interviews, and this is your first one. My only task is to decide whether you can be trusted to tell the truth, so your only task here is to answer my questions honestly. If you do not, I won’t give any indication, but I will write on your form that I cannot recommend you for clearance.’*

With that jagged shard in my throat, we began. She started by skipping fairly quickly through the main ‘risk’ areas: sex and relationships; family and friends; booze and drugs; gambling and money. Based on my answers, she decided what to hone in on, which in my case was sex, family and booze. The next three hours were by turns excruciating and exhausting.

Being unmarried, the first focus was less on fidelity and more on my history of sexual partners. She was testing susceptibility to honey-traps, how ready I was to bring strangers into my home, and where the risks lay of previous partners suddenly and suspiciously re-entering my life now I’d got this new job. She insisted on going through every bit of that history, from long-term relationships to one-night stands: names, locations, details, current status, etc.

She then went on to probably the worst 5 minutes of my life: this kindly spinster aunt – exactly as billed – listing every sexual practice you can think of and asking if I’d ever engaged in them. I won’t list her questions – this is a family blog – but my answers went something like: “No…. No….. No…. Erm, no…. No…. Yes, but only once…. No…. No…. No….. What is that? Oh, bloody hell - of course not…..”

It was a great relief when she moved onto family, but I realised then that all the background checks had kicked up some concerns. ‘Would you describe your father as an Irish nationalist?’, ‘What about his family?’, ‘How often do you travel to Donegal?’, ‘Do you meet your cousins there?’, ‘Have any of your cousins ever spoken to you about Irish nationalism?’

I knew what specifically she was driving at, and – rather than have it crushed out of me – I told her exactly what I knew about the 17 members of my extended Irish family who regarded the modern IRA as murderers, thugs and criminals, and the one bad apple who differed.

After all that, booze was easy. Unlike a doctor, she couldn’t care less how much I drank but just wanted to know where I drank, how loudly I talked, whether I took my briefcase with me, whether I ever lost things**, and most of all, could I remember how I behaved when actually drunk. My answers wouldn’t have been totally reassuring but they were honest, and –crucially – they were consistent with those my friend Anthony had given when she’d asked him that morning.

And that was it. She thanked me, I went away, and two weeks’ later, I was told I’d been cleared. What would I conclude that is relevant to the Andy Coulson issue? Well, all I know is this. If I had lied to that kindly woman with the half-rim glasses, she’d have known it in a heartbeat – so I’d defy anyone to go through that process and come through with their secrets still hidden.

* - There is a legendary story in Whitehall circles of the high-flying young diplomat who was given this instruction and took it so literally he thought nothing of confessing his ongoing £500 a week cocaine habit. The story goes that his interviewer said: ‘But you realise I can’t approve you if you’re currently taking drugs?’ ‘But I thought you just said to be honest’ said the diplomat. Clearance denied.

** - Coincidentally, the only time I did get drunk and lose any official papers, it was the mysterious application form I was sent by a specialist branch of government who were interested in inviting me to a further assessment process after I was accepted to the Fast Stream Civil Service in 1996. I called the number on the letter and asked them for a replacement form. They said they didn’t know what I was talking about and hung up.