Londoners have always loved to go to markets — some, such as Borough, have a history stretching back deep into the 12th century.

The international image of the London market was probably established (and immortalised) in the Disney film Bedknobs and Broomsticks in 1971. The whole world knows that “anything and everything a chap can unload is sold off the barrow in Portobello Road”. Most people have a favourite market, and mine, because it's most local to me, is the Friday and Saturday market at North Cross Road in East Dulwich.

But from Archway Market to Spitalfields, from Billingsgate or Greenwich to Barnet and Bayswater Road, a new type of market trader is emerging. The contemporary street trader is more likely to be a university graduate than a cockney barrow boy — and instead of selling plastic dustpans and packs of discount dusters will offer lifestyle products such as gourmet foods, eco-conscious fashions or sex toys made from organic wood.

In the past few months an even newer breed has sprung up. A market stall is an available option for starting a new career in a savage recession, and start-up costs are mercifully low. It's exciting to spot the birth of one of these new stalls — perhaps six pots of geranium cuttings apologetically arranged next to a cardboard sign, or a few bottles of homemade lemonade with handwritten labels.

You would be wrong to mistake these first attempts for a picture of desperation — in reality, they are signs of true grit, and the first bold steps into a better future. A baker who had a stall on Lordship Lane in East Dulwich two years ago, selling a few croissants and brioches with frozen knuckles of a chilly Saturday morning, is now the genial owner of Luca's Bakery, a glorious patisserie/coffee shop with a growing reputation across London. His old pitch has been taken over by two Japanese ladies selling boxes of excellent fresh sushi — if we're lucky, a sushi bar will open down the lane in a few months' time.

One of the thrills of going to a market is the possibility that you might get fleeced. It's an odd thought but I'm convinced that without the principle of caveat emptor (buyer beware) half the fun of going to market would evaporate. Using your wits and being a little on your guard, as well as haggling a bit before you buy, is an entertainment in itself.

Many new-style stalls, far from offering value-for-money bargains, are actually selling top-of-the-range luxuries at the proper going rate. Wander around the fine food markets at Pimlico Green and Duke of York's Barracks on a weekend in Chelsea and you could easily slip through £50 on a chunk of good cheese, a bag of sun-ripened vine tomatoes, a joint of pork and a few herbs.

It's becoming rare to find a stall manned by a toothless trader using cockney rhyming slang. In many markets you are more likely to find a stallholder speedily completing the Times crossword with a Montblanc, or dressed like a model in D&G.

One charming seller of extra-virgin olive oil in a west London market showed me her wares. “My husband buys up these lovely abandoned olive groves in Italy,” she said with a fluty Downe House or Roedean voice, offering me a drizzle of her spiciest first pressing. “He waters them and gives them some TLC and then he's off to the frantoio' — and here's our lovely oil,” she said, beaming.

Another change to market life is that often the new traders' main place of business is actually online — they set up a market stall so they can meet the public and get a response to their products.