Picture the scene. Trafalgar square full of people. Tony Benn's on stage, followed by people who have lost family members in Iraq. And various other speakers.

WWWWWWWWWWWWWWWWAY back towards the far rear side of the square a tiny little sound system on wheels, attached to bicyle is causing absolutely no nuisance at all whatsoever. And people are even dancing around it.

The old bill are standing around looking menacing. The music stops, the contraption is wheeled away and a rather angry bloke with a mega phone puts on a smile and thanks the police for "protecting democracy".

Well I've seen all this and I approach Mr Plod and ask him politely "Why did you make thing go away?"

So we had a bit of a discussion but in the end his colleague tells him they've got to go.

But apparently his superior officer had told him under some section something-or-other order to clear the square of pedal-powered sound systems. He told me there was "friction" between the people listening to the speeches and the people dancing around the thing. I told him I couldn't see any friction. He told me it was his job to keep the peace.

Plod offered me a few rather spurious arguments and then told me (without even a TRACE of irony) that, as the police, "it's our job to think liket that". (Yer telling me, I thought!).

And then, right... get this:

"Have you ever studied for an exam?"

Oh no, here we go. Typical, exactly the nonsense I'd expect when trying to reason with a policeman at a demonstration...

Well yeah, I've been through a quite a lot of exams in my life so far and I tell him this.

"OK, imagine you're revising for an exam..."

!!!!!!!!!!!!!!!! Aggghhh, but like he says, it's his job to think like that...

"...imagine you're revising for an exam and then a bunch of people come up and play music near you".

I told him I thought that was rather different. "Why?" He asked, perplexed. I told him that that would stop me concentrating. He said that the sound system might stop the people on stage from concentrating. "What would you do, how would you feel if you were up there giving your speech?" I told him that personally I'd be happy for people to do their own thing and that those who wanted to listent to me could do that and those who wanted to dancen around the pedal-powered sound system should be free to do that and that I wouldn't have a problem with that.

Well plod wasn't having any of that. He tried to sound reasonable by saying that when the speakers had finished and the bands started then the thing could come back and play music again but for the meantime it would have to wait.

Like he said, it's their job to think like that.