In my week: The contrast with doctor-lawyer-land is just too great: most of the people here look as though washing themselves is an effort, let alone washing their clothes

There's an old girl next to us, glumly studying a Welsh Mountain mare with a sweet little dished face. The mare's hooves are unshod, and sport cracks wide enough to lose a penny in. Nonetheless, with that optimism ponies drum up in the most thistle-fed of circumstances, she continues to poke her head through the bars of the gate and greet each grimy brat who offers her a bit of old hot dog roll.

Old girl, who actually can't be more than 40, roughly the same age as her acrylic sweater, addresses her companion, a Pictish redhead with a pushchair. "I hope," she says, "she doesn't go back to him or they'll probably kill each other. And the kids and all." Only she doesn't say that, because she contrives to cram five - count them, five - uses of the f-word into two sentences. Pictish companion clears her nose with a hefty influx of breath. "I hate her," she observes, and those Anglo- Saxonisms are an important part of her self-expression as well, "She's a stupid cow."

Such is Southall horse market, a metropolitan tradition about to celebrate its 300th year, auctioning the paupers and failures of the equine world to the ugliest examples of the human. You know those skinny skewbald nags you see, nosing the ragwort, from your train window? This is where they come from, where they go to, where, ultimately, they reach the end of the line. Here, opposite the cop shop, among a forest of sagging roof beams, corrugated iron and discount furniture warehouses, you can buy yourself a pony to keep on the allotment and still have change from a ton.

It's been one of those days where you keep feeling you've stepped off an aeroplane. Southall is a bit like that: a little country all of its own 10 minutes by train from central London but thousands of miles away emotionally. It's not Asia, though the area is scattered with Hindu God shops, spice shops, silk shops, pillow-sized sacks of basmati, chaat houses and shops selling piles of sequinned open-toed sandals.

Claire and I have spent a lovely afternoon collecting plastic bagfuls of cloth - embroidered red silk, green brocade, silver lycra velvet, yellow- and-pink mimosa print, and more Imeldas to swell our shoe racks. We've lunched on chickpeas and pancakes and little heaps of grated coconut, and had a nice chat about herbal medicine with the owner of the restaurant. Walking eastwards along the High Street, we've turned up the alleyway marked in the A-Z as a market, and it's been like stepping into the country where everyone marries their cousins.

The contrast with doctor-lawyer-entrepreneur-land is just too great: most of the people here look as though washing themselves is an effort that's beyond them, let alone washing their clothes. There is the odd flat-capped, tweed- jacketed countryish old boy leaning contemplatively on a fence, the occasional face that would look great on a poster for the gypsy-caravan holiday idyll, but most of the men strutting among the piles of droppings and pursing their lips at the RSPCA inspectors obviously share bloodlines with Fred West: mops of frizzy hair over faces whose creases are etched in black, dachshund bodies on bowed, foreshortened legs.

"Good God," says Claire, "where do all these people come from?" I know what she means. The last time I saw this many ugly people in one place was in the villages around Wadi Rhum, but at least the Bedouin have thousands of years of relative isolation to explain their appearance. Where these people hide in the big city is a mystery: you certainly never see them in groups, not even at football matches. Everyone shows signs of inherited disorders: underhanging jaws and overhanging jaws, missing teeth, watery blue eyes, unnaturally large hands, bum-fluff coating lips and jaws. The scene has the greyness of a Pathe newsreel film of life in the East End before wartime food rationing improved the British diet beyond all recognition.

A couple of tiny ponies in a stall with a larger piebald start squealing and kicking, and a crowd gathers, faces lit up with the pleasurable prospect of a free cockfight. The auctioneer takes to his tiny brick booth, switches on the sound system and starts taking bids as horses and ponies, broken- down ones, unbroken ones, ungroomed ones, are whipped and slapped into trotting out. Prices go up in increments of pounds 1 and pounds 2; a little palomino gelding goes for pounds 62, a spotted colt for pounds 77, a Shetland mare and foal for pounds 190. And I really, really want to leave, to close my mind to the depressing thought that, in the end, if you're born poor enough, or ugly enough, or unlucky enough in this country, you still have little more chance of improving your lot, of escaping cuffs and cusses and the prospect of being sold and sidelined, than you did back in the days when this market first came into being. Remember that when you vote on Thursday.