Shouldn't all market traders look like Richard Dinwoodie - more George Clooney and less Ray Winstone? He is declaiming in detail, the properties of Ventnor Oyster Stout. His potential customer, a lawyer from Dorset, has driven more than 100 miles to London to buy oysters from the Isle of Wight - and the appropriate beer to go with them.

Another punter has bought venison sausages, which he plans to accompany with Braveheart Ale, from the Moulin Brewery of Pitlochry, Scotland. "You could also poach the sausages in the beer," suggests Richard.

It is rare to see so many beers on a market stall, but at his stall in Borough Market, in London, Richard stocks more than 250 types: Secret delights of British brewing rub shoulders with a chestnut lager from Corsica, a genuine small beer from California, and a stout from Sri Lanka.

This is one of the best selections in Britain. Richard and his partner Mike Hill are knowledgeable and enthusiastic. They met at a student pub run by Richard, and originally obtained an occasional licence for the market stall. Now the lowly stall, Utobeer, has spawned a wholesale business.

The market is where Utobeer meets its natural customers: people who take it as read that a love of food and drink inevitably embraces beer - the wine of our country. The same eclectic beer lover will be at The Great British Beer Festival next week at Olympia, London, from 5-9 August. And no doubt some visitors will make a detour east to Borough Market.

Just as Paris has its right and left banks - its salubrious and salacious sides - so London is rediscovering its polarities. Here, the north bank was regulated as the City; the south bank, the Borough, was permissive, and Flemish immigrants - surely the model for Shakespeare's Falstaff - brewed for inns that accommodated music, dancing and strolling players.

Later, Borough was the centre of the hop trade. The use of the hop had been introduced to England by the Flemish. Cultivated in the southern counties, the harvested blossoms entered London via Southwark. The Hop Exchange building, decorated with moulded façades of the vines, stand as a testament to the growth and success of the industry.

One of the old Southwark breweries was owned by the Jenner family. Today, Miles Jenner is one of Britain's most respected brewers. His beers are on tap at The Royal Oak, in Tabard Street, about ten minutes' walk from the market. This jewel of a pub is open Friday evenings but usually closed Saturday and Sunday. The brewery is in Lewes, and uses a significant proportion of Sussex hops.

Following years of depression, Southwark is gentrifying in parts, as evidenced by the growing popularity of Borough Market. What draws people is the knowledge of the stallholders and the diversity of the produce.

Even the mid-market pint offers extraordinary choice. The Market Porter, on Stoney Street, used to provide sustenance for the workers on the Jubilee line extension. When that was completed, landlord Tony Hedigan had to rethink his business. He concentrated on guest cask ales. Knowing how temperamental ale can be, he followed the wise policy of ordering very small casks. He looks after his beers beautifully, and offers 120 beers a month - mind you, some only last an hour.