Having written a new book, The Rotten State of Britain, to show what a police state we have descended into, I seem to have become a victim of it myself.

This morning I was doing an interview with a Canadian TV crew on the outcome of the G20 at my office just underneath the Church of England's headquarters in Westminster. After I'd told them that capitalism was still alive and well and that the mess we're in was a failure of government policy rather than banks or markets, they decided they would like some set-up shots outside.

So the cameraman lugged his enormous camera and tripod onto Great Smith Street and I started doing my stage walk towards the office door. Whereupon a red police car, lights flashing, screeched up and two officers rushed out, in full body armour, to confront the cameraman and the interviewer and ask them what they were up to.

The cameraman suggested that it was pretty obvious what they were up to – setting up a TV interview. The police officers took out their notebooks. The cameraman ventured that this was not really necessary, but the police replied that under Home Office guidelines – the department run by the keeper of the nation's morals, Jacquie Smith, of course – they had to report that the crew had been stopped. And since we were under the gaze of at least ten CCTV cameras (five on the Schools department and even more on BERR), they had to go through the paperwork. They stopped anyone 'behaving suspiciously' around 'sensitive buildings'. Is the Church of England's headquarters really so sensitive? Am I worried about them taking pictures of my office, when it was me they were photographing?

So the crew had to provide identity and state their date of birth, their height, and even their ethnicity and were duly given their yellow copies of the stop and search form.

It really does underline the fact that we are now living in a police state, which is exactly why I wrote The Rotten State of Britain. One smart comment or false move and we could all have been arrested and held for 21 days as terrorist suspects. It's exactly why I wrote the book. The police used to be our servants. Now they're our masters. No doubt they get a bonus for everyone they stop; senior officers certainly do get a bonus for everyone they caution or charge. Fortunately, the police are drowning in paperwork so they can't do too much harm. But I wish they were out there catching burglars rather than stopping people from doing their job.