I'm sitting in traffic on Chelsea Bridge Road and suddenly the world's exploding

For the first few seconds, I don't know what's happening. There is a skull-bursting bang and my body judders up and down, backwards and forwards. Something hurts, but I couldn't say what. There's a hot feeling in my stomach. I'm sitting in traffic on Chelsea Bridge Road and suddenly the world's exploding - above, below, inside, under me. A shivery sound of breaking glass; particles of shock and smoke hanging in the air. Everything (child car seats, maps, rubbish) has been hurled to the floor. Ridiculously, I pick up the newspaper, replace it on the seat.

I get out. The car behind is a dirty, brownish maroon, its front crumpled like a Kleenex. The rear of my car has a V-shaped buckle, the exhaust trails on the ground, the lights resemble chewed-up, spat-out boiled sweets.

The driver who crashed into me gets out and just stares. There is a blonde woman, fortyish, in his passenger seat. "Are you a mini-cab?" I ask him, as if we were playing Botticelli. He nods, but I'm stuck for the next direct question.

The man in the car in front of me - something low and silvery and expensive- looking (into which I was briskly shunted) comes over. "It wasn't me," I begin.

"Don't worry." He's wearing a suit, has friendly eyes.

The blonde woman gets out of the mini-cab. "Does anyone have a mobile?" she demands and sinks abruptly to her knees. We rush over.

Traffic on Chelsea Bridge is at a virtual standstill. A police siren screams in the distance. Two young men in lumberjack shirts and hats with earflaps beam themselves in from nowhere.

We move the woman to the pavement, her slender, stockinged legs stretched out helplessly in front of her. Crisp bags dance around her ankles in the October wind. "I'm a doctor," she sobs. "Going to an emergency - life and death - they don't speak English - got to phone."

"You're in shock," says the silvery car man. "We'll get an ambulance.'

"But I'm a doctor" - she throws up her hands.

"Sorry, but you need an ambulance."

"It's an emergency. They're waiting for me."

"Give me the number," I say. "There's a call box." I take the Filofax that she holds out to me with shaking hands.

"Speak to Damien," she says. "I tell you, it is life or death."

Cars are edging politely past around our accident. My ears hum as if I am under water. One of the lumberjacks is phoning for an ambulance. When he's finished, I dial. "Damien? You don't know me, but ..."

Back on the pavement, I reassure the doctor that Damien is on the case, but she is oblivious. "Shock," someone says. "And she may have banged her head."

"Are you all right?" the silvery car man asks me gently. Now that Damien is dealt with, my limbs are reduced to a boneless state. I shake all over. "You ought to sit down," he says. I look at the pavement, but I've got my brand new scarlet coat on and anyway I'm not sure I'd get up again.

"I'm OK."

"Wait till tomorrow morning before you decide that," says a policeman who has appeared at my elbow.

I can't shake myself back into the world. Everything is too quick, shiny, too - well, obvious. There are now four toy policemen, one in Day-Glo on a neat Playmobil motorbike, ambulancemen in Peter Pan green squatting down on the ground. Stretchers, oxygen masks, broken glass and crushed metal everywhere, all drowning in bright autumn sunshine.

"Were you in a hurry?" I hear my voice asking the silvery car man.

"Um, just off to get my hair cut. My girlfriend and I are going on holiday to France. And you?"

"What?"

"In a hurry?"

"Oh no. Just driving." My various intended errands seem to belong to another world. I'm suddenly very cold.

"Have you got someone who can recover this vehicle for you?" one of the policemen asks me. "AA or someone?"

I say: "Green something ..."

I unlock the door and fumble in the glove compartment. Dusty, flattened nappies and half-sucked sugar-free lollipops cascade out.

"Green Flag?" The policeman looks impressed. "Just signed up with them myself. Supposed to come within an hour or you get 10 quid."

"Some pizza delivery companies do that," offers a lumberjack.

The doctor is stretchered and slid into the ambulance. The police give us all little slips of green paper.

"I'll get along then," says the silvery car man. We shake hands gravely.

"Have a good haircut," I mumble.

He looks at his watch. "Might have to give that a miss now." I realise the accident happened more than an hour ago.

The mini-cab driver stares into the middle distance. I haven't heard him say a word the whole time. "Are you sure he's all right?" I ask the policeman.

"Looks all right, doesn't he?"

"Does he?"

Green Flag arrives (an impressive 20 minutes). As my wreck and I leave the scene, the man is still sitting in his car waiting to be towed off. His expressionless face is devastating.

At home, Jonathan calmly inspects the damage. Part of why I love him is he couldn't care less about cars. "Only a lump of metal," he shrugs. "Though, admittedly, an unusable one now."

It's been a week of living dangerously. Sunday, I sat on a wasp; Monday, I pierced my foot on a sliver of broken Power Rangers mug; Tuesday, I scalded myself on a boiled egg; Wednesday I tripped over the cat and broke a banister with my knee.

We agree the best place for me is bed.