DRINK / The local down in your pint: When the French wanted to learn about the different styles of British beer, they consulted the expert. This is what Michael Jackson told them

France's grandly named Conseil National des Arts Culinaires does not restrict its attention to frogs' legs and Bordeaux wines; it concerns itself with beer, too.

As part of a European study of regional comestibles, discussed on these pages recently by Joanna Blythman, the Conseil asked me to identify British styles of beer that might be protected by designations of origin.

Elsewhere in Europe, certain brews already have such protection. In Belgium and the Netherlands, for instance, the term 'trappist beer' may be used only to identify the ranges of strong, sedimented brews made by half a dozen abbeys of that order. The Belgian beer style Lambic must by appellation contain at least 30 per cent unmalted wheat, and be fermented with wild yeasts.

In Germany, a beer may be called a Munchener or a Dortmunder, for example, only if it is brewed in the city whose name it bears. Kolschbier, the local style of Cologne, must be a golden ale, and regulations govern not only its method of production, but also the shape of the vessel in which it should be served.

In the British Isles, we are hazy on designations of origin and do not regulate appellations of style, but we have hung on to regional differences among our beers. Even within the single-style bitter, very dry examples are most commonly found in the South-east (Shepherd Neame in Kent; Brakspear's in Henley; Gale's near Portsmouth; and Young's in London). This may be because the South-eastern breweries are nearest to the hop gardens of Kent and Sussex, and the traditional Kent hop variety, Goldings, gives quite a dry character.

In Hereford and Worcester, where they are called hop 'yards', the principal variety is Fuggles, which imparts a softer touch.

In Staffordshire, the water of Burton, with its calcium sulphate, favours pale ales. The water influences clarity and crispness. These beers gained an additional dimension of fruitiness from yeasts that work in a system of linked wooden barrels, known as Burton 'unions'. In Nottinghamshire and Yorkshire, some beers gain a notable creaminess because their yeasts inhabit a system of double- decker square vessels. They are also quite malty. The farther from the hop gardens (or yards), the more the beers lean toward the sweetness of the malt.

The North-east specialises in malty, nutty-tasting brown ales such as the famous example from Newcastle. The same region makes yet-darker ales identified locally as 'Scotch'. Traditional London styles such as porter and sweet stout are also made in the North. Nor are all dry stouts Irish.

When I discussed some of these distinctions with the Conseil in Paris, all attracted interest, but especially those that depended upon yeast and fermentation.

Yeast is a potent influence on the flavours of all fermented products, but this has been fully appreciated only in recent years. All yeasts, which are living organisms, are descended from the wild, and some are very regional in character. Their nature is further shaped by the vessels in which they live and work.

The Burton 'union' system survives only at Marston's, but several breweries in Nottinghamshire and Yorkshire still have that region's squares. The softly creamy beers of Hardy and Hanson in Nottingham are made in stainless-steel squares. So are the firmly smooth products of the Mansfield Brewery.

Within Yorkshire, Tetley's of Leeds uses metal squares for its creamy bitter. Nearer to York, the small town of Tadcaster ('second city', after Burton, in British brewing) has Samuel Smith's. This brewery uses stone squares to make its maltily creamy ales. Once, Yorkshire sandstone was employed. Today, Welsh slate is preferred.

Those who enjoy a creamy Yorkshire ale, or simply value regional differences, were delighted when the Black Sheep brewery was established in Masham, near Ripon, in 1992. The new brewery added to the list of stone-square beers.

In the Yorkshire square system, the turbulence of fermentation forces the liquid to circulate between a lower and upper chamber. This trains the yeast to work slowly, leaving much of the body in the beer and imparting a well-absorbed carbonation. That Yorkshire creaminess is enhanced when the beer is served through a tight nozzle at the pub.

It has been suggested that the Yorkshire square system was developed with the help of Joseph Priestley who, in 1722, delivered a paper to the Royal Society on the absorption of gases in liquids. In addition to being a scientist, and later a political dissident, he was for a time the minister of a Unitarian church in Leeds. During that period he lived next to a brewery on a site that is now Tetley's.

If the trappist monks of the Low Countries can have an appellation controlee for their beers, perhaps a Unitarian God would wish the same protection for the 'square' ales of Nottinghamshire and Yorkshire.