'Sweat is now pouring down my face. They think I'm lying because I'm perspiring so much'

In all my years as a writer, I have only twice been invited to read my work in public: once last year at my children's primary school on Book Day, and once this year at my children's primary school on Book Day. In my opinion, you have not been fully baptised into public speaking until you have read a portion of your novel to 30 unblinking eight-year-olds.

This year, though, I was addressing Class 5, most of whom are either 10 or pushing 10, and I planned to read them an old and very short piece about eating dog food. I don't normally like to remind people that I once ate dog food for the sake of 600 words, but this time round I was desperate to entertain the children rather than bewilder them.

The only problem was that the piece had the word "friable" in it. I didn't know what friable meant until I was about 30, so I figured they wouldn't, either. I tried to think of a simpler word that conveyed the same meaning in this context. I thought about leaving out the whole sentence, or rewriting the entire piece in more child-friendly language.

And then I thought, no - I'll just teach them what "friable" means. Why not? I will walk in and write FRIABLE on the board. I will ask them what they think it means, and they will say something like "Able to be fried" and I will shout, "No! That's what I thought until I was 30!" It will be both fun and informative.

There are some difficulties with this idea - I have no presence, no teaching skills, no inherent sense of fun and no particular way with children. I am also prone to panic. But I am not thinking about any of this on Book Day, because I am so late.

In the morning I had come up with what I thought was an innovative journey plan - drive to convenient station, get on tube, conduct business in central London, take tube back to car, drive short distance to school - but I could not find a parking place anywhere near the station. I am meant to be at school at 3pm, but at 3pm I am still on the tube, experiencing delays. I run a quarter of a mile back to the car, drive to school and run down the road to the building. I arrive 20 minutes late, bursting into the classroom and interrupting the game the children are playing.

Everybody sits down and I slowly write FRIABLE on the board, trying to catch my breath. I ask them what they think it means.

A child says, "That something can be fried" and I shout, "No!" a little too triumphantly.

Then I feel the sweat start to crawl through my hair. I have run a long way and the room is incredibly warm. I tell the children that friable means "capable of being easily crumbled", and they look as if they don't believe me.

Sweat is now pouring down both sides of my face. They think I'm lying because I'm perspiring so much, I think. When I finish reading the piece, all their questions seem to touch on my veracity. "Did you really eat the dog food?" asks one. "Did that really happen?" asks another. One girl asks a question, and then as soon as I start to answer, she puts her hand straight up again, as if I've already said something untenable.

The bell goes, but the questions keep coming. "Was that a true story?" "Was the person in the story actually you?" Perspiration is stinging my eyes and gathering in the runnels of my ears.

At the teacher's insistence there is one final question, followed by some polite applause. In the silence that follows, one kid says, "Is that sweat?"