I am handed a glass of something murky by Isabelle Legeron MW (see her website, thatcrazyfrenchwoman.com, to find out more). "You're going to hate it," she smiles, like a nurse administering an antibiotic. In fact it's Akmenine, more a probiotic cross between scrumpy and the bitter aloes mum used to apply to my swollen thumb. It tastes OK; it has character. The 2008 Sebastien Riffault Sancerre is the first wine chosen by Alice Feiring, a natural wine evangelist (see her blog, The Feiring Line), to illustrate her talk at the inaugural natural wine fair last month in London's Borough Market.

"What could be controversial about wine that has nothing added and nothing taken away," avers Feiring. It's a good line. Next we taste a 2009 Montesecundo, refreshing in its light, cherryish sangiovese fruit with its rustic, made-for-pasta texture. Then an extraordinary 1997 Vin des Voiles Gaillac made from mauzac rouge. This is not Gaillac as you know it, but with its marmaladey, sherryish whiff and salty tang, more like a vin jaune from the Jura, appetisingly dry and valid in its own right, albeit left field.

The fair was buzzing with anticipation that Sunday afternoon, and, by all accounts, on the following two days as well. The wines were supplied by Caves de Pyrène and four other importers. Far from being cloudy and oxidised, the overall quality standard was high, the character exceptional. There was Michèle Aubery's spicily aromatic syrah, 2010 Domaine Gramenon Sierra du Sud, Côtes du Rhône, an intense blackberryish 2009 Le Roc des Anges Segna de Cor, Mas Bruguière's succulent 2008 La Grenadièr, a savoury, characterful 2006 Vinci Coyade and nuttily intense 2008 Matassa, both Côtes du Roussillon whites. There were two fine Saumur reds in the delicately herbal 2010 Filliatreau Château Fouquet and Thierry Germain's intense 2009 Saumur-Champigny, Terres Chaudes.

Alice Feiring's talk raised questions such as just how natural is natural wine? Should it have a rule book like organic and biodynamic wine, and how oxidised or cloudy (both the bugbear and signature of some natural wines) can a wine be before it's unacceptable? Supporters point to natural wine as a breath of fresh air, an antidote to big brands and the cynical commercialism of the wine industry, an idea whose time has come. Detractors find it woolly around the ears, and fuzzy up the nose, for its lack of definition.

You don't have to be either pro- or anti- to see that natural wine is a wine movement that's captured the spirit of the age. Provoking and inspiring people to talk about and taste it has far more impact than May's worthy National Wine Month campaign. And it's not all about French wines. I tasted a deliciously peachy, textured 2010 Afros Loureiro Vinho Verde from Portugal and I ended up at a table where a Sardinian producer, Gianfranco Manca of AA Panevino, had four distinctive reds for tasting. Baffled by the labels, I had to ask what they were called. "Well, they don't really have a name as such," he said (in Italian; someone helpfully translated). "The dialect on the label tells you which corner of the cellar each one comes from." Who needs marketing when you're part of the natural wine movement?

For full details, contact Les Caves de Pyrène (lescaves.co.uk), Yapp Bros (yapp.co.uk), Aubert & Mascoli (aubertandmascoli.com), Wine Story (winestory.co.uk) and Dynamic Vines (dynamicwines.com)