E Jane Dickson: 'I am rooted to the spot with urban dread'

Oh joy. I've just found a note in the book bags informing me that, as part of its Healthy Living initiative, the school will be holding a family t'ai chi session at the crack of dawn on Primrose Hill. Clara and Conor can't wait.

"You'll like it, Mum," says Clara, encouragingly. "You don't have to move much. It's hardly like exercise at all."

"Yeah!" confirms Conor, "I saw it on Blue Peter. You kill the baddies really, really slowly, and you get this big stick and jump over it..."

"I think maybe you're thinking of tae kwon do," I suggest, although frankly, for my money, it could just as well be Typhoo. Martial arts aren't really my thing, but since Con got a pair of karate-style pyjamas, he is something of an expert.

Bedtime, these days, is a sterner ritual, involving dignified bows rather than hugs. "Do not kiss me," warns Master Con, in a sinister Oriental wheeze, "I am Ninja Boy. This," he says, pouncing on me from behind, "is 'The Way of the Cat'."

"And this," I tell him, propelling him bodily along the hall, "is 'The Way of the Bathroom'. Don't you know that Ninjas lose their powers if they don't clean their teeth?"

Con shoots me his "don't start your nonsense" look and proceeds, with an assassin's stealth (marred only by the 'Hi-yaah! Ka-pow! sound effects) to the sink. I am unwilling, however, to lose out on a good moral, and scroll through the little I remember from Teenage Mutant Ninja Turtles about martial-arts ethics. "It's not just about whacking baddies," I tell him, "it's about using your strength and your mind to combat aggression. With Great Power comes Great Responsibility. That kind of thing."

"Actually, Mum," says Con, "that's Spiderman." But he assures me he knows what I mean.

The following day, aggression comes looking for a fight. We stop off to buy grapes on the way home from school and Conor and his little friend Gabriel are diddling about in the porch of the fruit shop, when a man, possibly drugged, certainly demented, shoves past and swears foully at the boys for getting in his way. My first reaction is to herd the boys back into the shop, but Gabriel's mum is made of sterner stuff and takes the man to task for using such vile language to children.

The madman rounds on my friend, pumping out foam-flecked, four-letter abuse. I know I should rush to her aid, but I am rooted to the spot with urban dread, that "Oh god, this is the one, this is the loony with the knife with my name on it" reflex of London living, and the best I can manage is a barely voiced "Look here...".

In a matter of moments, though it seems much longer, the bully backs off, and, shamefaced, I congratulate my friend on her courage. "I'm sorry I was so useless," I tell her. "I didn't think I scared so easily."

Later that night, Conor is replaying the incident. "How could you be scared, Mum?" he wants to know, "when you had me and Gabriel to protect you?"

"Thanks, Ninja Boy," I tell him, and he doesn't object when I drop a kiss on his head. Privately, I resolve to make the t'ai chi class after all. My chi can do with all the help it can get.