The current trial of pop star Cheryl Tweedy for racially aggravated assault for some reason reminded me of my own brief, shameful and, thankfully incompetent, contribution to racism as a teenager. It reared its head on two separate occasions around the age of 14 - one unwittingly, one unfortunately not.

The former was just a case of me joining in with the laddish heckling of an Asian woman, who was actually the best (or at least the most effective) physics teacher I ever had. Her name was Mrs Khan, but the bad influences in my class (spoiled, streetwise, middle class lads the lot of them) decided it would be a hoot to shout "Mrs Coon" in the middle of her lessons.

Me, I was seeking approval from my peers, and very much like the others - except for the streetwise bit. I had no idea that coon meant what it did, and it was the last thing this kind, patient, intelligent woman deserved. I just thought I was saying something funny and buying credibility by fitting in. When I found out what I'd been saying... well, I don't think I need to tell you anything other than I didn't feel good.

The second incident came just a few months later. Despite having my own friends, I wasn't one of the in crowd, the cool guys, still an outsider. I was walking by myself through the school grounds, and passed three lads from my year, one of them bouncing a tennis ball. Several seconds passed as we walked in opposite directions. And then suddenly the tennis ball hit me in the middle of the back.

Furious, I turned and screamed, "You black bastard!" at the lad who I'd seen with the ball, and threw it back at him (though, this being me, it missed). I've no idea whether Tanveer Raja, the fairly reserved Bangladeshi boy I was accusing had actually thrown the ball, or whether it was one of his far less palatable and more aggressive white friends. Feeling persecuted, my pride hurt worse than my body, I lashed out at the first thing I could latch on to, the one time I've picked on someone's colour for pejorative purposes.

What I do know is this: not only did I insult Tanveer with a general racist slur, I also disrespected his personal ethnic background and lumped him in with all people of colour. And although he didn't retaliate in any way, the resulting self-inflicted shame and guilt were far too much for me to cope with. I had to confess to my parents the same evening, and they were every bit as appalled as one might hope.

Eventually, Raj and I were able to talk again although we never were (but never had been) close.

But the whole. sole experience was more than enough to teach me a lesson I shouldn't have needed to learn.