There are two good uses for your car's horn. One, the gentle prod, is to encourage the person in front of you to notice that the lights have turned to green. The other good use, the louder one, is a way of saying 'please don't kill me'.

There are more bad uses than good ones. They range from the 'pa

rp parp' that says 'I'm a fat, idle minicab driver who can't be bothered to get out of my car and ring your doorbell' to the 'paaaaaaaaaaarrrrrrrrrrp' that says 'oops, that overtaking manoeuvre really wasn't such a good idea'.

I rarely use the horn. I'm never sure how hard you need to press to get a 'parp parp' rather than a 'paaaaaaaaaaarrrrrrrrrrp', and in any case the person whose attention you're trying to attract usually ignores you, while the people who do hear you never seem very pleased about it.

But I was driven to administer a vigorous parping yesterday. I was attempting to cross a big, busy roundabout. There was clearly some sort of problem ahead, and we were all shuffling forwards a few feet at a time, sometimes giving way, sometimes barging in. It was progress of a sort.

Until I came up behind someone in a VW Lupo whose response to such severe congestion was to just sit there, doing nothing. If he'd gone a foot to his right, I could have moved. If he'd gone a foot to his left, a Transit could have moved.

But he did nothing. Oblivious, paying no heed to the consequences of his actions - or, in this case, inaction - for the people around him.  So I hit the horn. He did nothing. So I had to just sit there, and so did the bloke in the Transit. For all the Lupo driver cared, we'd still be there now.

Eventually, the jam became a little less sticky, like they always do, and we all got to where we were headed. But I hate the fact that inconsiderate drivers can so easily bring us all grinding to a halt, and I hate the fact that I was goaded into becoming one of the noisy blighters who sits there honking his horn for no good reason.