Security is a paradox. We all want to be secure, but we are deeply suspicious of the apparatus needed to make us so. In this, I am no different from the next man. In Britain, it’s said, we are subject to more scrutiny by CCTV than any comparable nation. Most of the time we don’t know that “they” are looking in on us; when we do, we soon forget it. After all, the argument runs, if we’re not doing anything wrong, what do we have to fear?

This scrutiny extends not only to street corners and public transport, but into our workplaces. There was a time when security in colleges was conspicuous only by its absence. If trouble broke out, the principal would descend from his office and sort it out. If the offenders were especially desperate characters, he might even have to use a little sarcasm.

Those days - for most colleges, at least - have long gone, and the security professionals have moved in. Entering the building is like getting into the Baghdad Green Zone. And once inside, the cameras are there to record your every move.

This came home to me recently when I found myself starring in a college production of You’ve Been Framed. On my way across campus I turned a corner and was suddenly presented with a dilemma. Up ahead was a barrow stacked with goodies for the canteen: sweets, crisps and soft drinks.

There was also a young man about to help himself. By the time I reached him, he had got through the outer packaging and freed up a can of Coke. He wasn’t anyone I knew. In a large college with thousands of students, that’s common enough. Nor did I know his three friends who were standing around, egging him on. It’s at times like these that you notice how big the average 18-year-old has become.

There was no one else in the corridor, and I needed to make an instant decision. My inner Clint Eastwood had no problems at all. “Go ahead,” I would say, “take the Coke and make my day.”

Sadly, though, in these politically correct days, college lecturers are no longer routinely issued with Magnum handguns. There was also the little problem that my inner Clint Eastwood tends to get overruled by my outer Woody Allen.

So what happened? You might call it the classic compromise. I put my hand on the drinks can and said: “You don’t want to take that, do you?” Now the person with the dilemma was the would-be thief. I had offered him an easy way out. But with his mates watching on, could he afford to lose face?

In a moment it was over. The can was back in its place and the four were off up the corridor. Maybe I should have chased him, rugby tackled him to the ground and screamed for back-up. But in the end nothing had been stolen. And you could argue that temptation had been put in his way.

I went and found the canteen manager and suggested it may not be a good idea to leave his stock unprotected. He said he’d only left it for a moment while he went for a key to the store room.

What didn’t occur to me, however, was that the whole episode might have been caught on camera. A day or so later, the security manager took me to one side and said he had something to show me.

There I was, in the middle of the shot, looking grey and grainy and not at all like Dirty Harry. And there they were, the light- fingered foursome, legging it up the corridor. Did I know who they were? he asked. I didn’t. Would I recognise them again? That was a tough one, I said, it all happened so quickly.

To be fair, he didn’t question my actions. But it certainly made me think them through again. It also made me realise that what we may think of as private decisions, may be private no longer.