My Mum rings up. "I tried to ring you yesterday," I tell her.

"We went to one of those medieval banquets," she says. "Have you ever been to one?"

I laugh. "No, what're they like?"

"Pretty awful, really," - she pauses; click of a cigarette lighter, intake of breath - "You just sit there and eat appalling food in the dark."

"Like what?" I'm intrigued. "Pigs' heads and things?"

"Nothing so glamorous. Spare ribs. A whole small chicken. You get a dagger by your plate - and men dressed up and shouting things into microphones the whole time you're eating, such a racket. You can't talk or anything - a total waste of time, really."

Chloe, standing in just knickers and a Spiderman mask, pesters for the phone. My mum evidently asks her what she wants for Christmas, because Chloe straightaway replies: "The shaving man."

"It's Ken - Barbie's boyfriend," I explain as I retrieve the receiver. "I haven't seen him, but I think you can shave him or something."

"But has she got a Barbie?"

"No," I reply, nostalgically remembering my stepbrothers' Action Men - all greenish fuzzball heads and scars and limbs that folded every which way and clung valiantly to bunkbed ladders. "But she really likes Ken."

"Well, check she's sure about it," says my mum.

So we decide to go to Peter Jones's toy department (benignly fuddy-duddy, Never Knowingly Undersold, never raucous like Hamleys or depressing like Harrods) to have a preliminary look before making our lists for "Father Christmas".

As we leave the house, we blithely step over the cream cracker that's been on our garden path for at least three days (since the dustbin men came). As always, Raphael tries to pick it up. "No, don't, it's dirty." I'm sure it's not ours - we don't have cream crackers - I suppose I'll have to pick it up eventually.

We cruise for a meter and find one on Draycott Avenue. It's a bright, cold morning - sky from a paint catalogue - church bells ringing somewhere. A man walks briskly by in a morning suit, mauve jaw that looks like it's been patted with cologne.

We get out of the car and I inspect the meter, while Jacob tells me a lengthy joke (he hasn't yet acknowledged the need for a punchline). A thin woman in high clip-cloppy heels passes us, gripping two leashes with rat-size dogs on the other end. They skitter along, vibrating as though battery operated, sporting matching knitted jackets with a pawmark pattern.

The children screech with delight - until one of the dogs squats in the middle of the white pavement and deposits a small, black, constipated turd. "I hope she's going to pick that up," says Jacob loudly. The woman gives us a flinchy, narrow-eyed look.

"Cruella de Ville," screams Raphael aptly, making a fist. I try to herd the children along the pavement, but he braces himself and whips out his next-best phrase: "Pants on fire!" With a snarl, the woman clops off.

In the toy department, Chloe and Raphael stand close up against a tiny video screen watching Sing-Along Songs featuring the rigid-breasted and terminally hungry-looking Pocahontas, while Jacob manages to go around falling in love with toys that all say "eight years and over" on the box (he's seven next birthday).

Even the Playmobil Gold Mine which, three months ago, he moaned and mooned over for weeks, has lost its magic now that Christmas looms so greedily, plausibly real.

Chloe fingers the cellophane on the box of the "shaving man", as well as a tiny (expensive) loo for her Sylvanian Families; Raphael is most attracted to things he's already got at home: familiarity breeds adoration, not contempt, in the under-fives.

As we take the lift to the basement, Chloe panics: how on earth will Father Christmas see her list? Suddenly reluctant to rely on the Royal Mail, she decides Daddy must nail it to the roof - "Absolutely flat, a nail in each corner," - so FC can read it as he flies over.

"He'll swerve and crash," says Jacob who, though still a believer, is nevertheless coming up with rather a lot of practical problems this year. "Then he'll be in casualty on Christmas Eve all because of your note, then how will you feel?"

"Of course he won't crash," I soothe, protecting my four-year-old from this merciless onslaught of TV realism. "Have you ever heard of him crashing - ever?"

"Have you ever heard of anyone nailing a list to the roof?" counters Jacob.

Down in the basement, I buy some plugs and bulbs and the kids writhe on the lino floor, fighting. Raphael pokes Jacob close to the eye with a plastic drinking straw - where did he get it? - and Jacob bursts into tears. Sloane Square women in gilt-buttoned suits (who undoubtedly keep ratty little dogs at home) step over their bodies without a glimmer of amusement. I apologise, but secretly applaud. At least my children don't mess up the pavements.

Back home, a desolate, wintry darkness is descending and it's not even lunchtime. Cars lined up along our road seem forlorn and tired - hollow tin things with a veneer of dirt. A woman in an ankle-length turquoise veil runs up the steps and into the refuge centre opposite. Further down the road a car revs and revs, clouds of exhaust billowing like stage smoke.

It's been raining and our garden path shines darkly. The cream cracker's still there, but someone's taken a bit out of it. I exclaim at this. "No, Mummy," says Jacob wearily. "The bite's been there all along."