It could be any fast food transaction, anywhere in the world. I walk through the door and up to the counter where a beaming American in a stripy cap greets me. My mind goes blank. Big Mac and fries? No, I remember. "Triple-wet-skinny, please." She taps it into her till. "Anything else?" "Chocolate muffin. Take away."

After a few moments' inimitable hissing and shussing, she hands me a paper cup, lid on, and paper bag, muffin within. "Have a nice day." I am. I leave.

This is coffee and cake in Covent Garden. I have just visited one of three Seattle Coffee Company bars. And there are plans for lots more, following on from the mass-market revolution in the US, rather glibly known as ESBAD - espresso-based drinks - that began life in Seattle in the Eighties. It is forecast that there will be 10,000 of these bars in the States by the year 2000.

To some extent, Aroma Cafe have proved the popularity of this formula, with their blend of American-style coffee bar and European cafe. They now have nine outlets in London where you can indulge in milky lattes and mochas.

The Seattle Coffee Company has already signed a deal with Waterstone's to open ten cafes in their bookshops around the country. Another American concept, bookstore cafe - feed and read - is big and coming our way. It is also widely rumoured that Starbucks, the largest chain of coffee bars in America, will shortly do a transatlantic hop. Other operators are bound to follow. It's enough to keep anyone awake at night. You can only drink so much coffee.

All the forthing and hissing is a distraction from a simple concept; the adoption, modification and repackaging of the classic Italian espresso for the masses. Agreed, a connoisseur can expect an extremely good espresso, albeit it in a paper cup, in such a bar. Cleverly, though, these marketeers have also trapped the "creative" coffee drinker who dislikes espresso. So you can have it long, milky, frothed or foamed, and flavoured with tiramisu or toasted marshmallow syrup. And there's Lego-type language to go with it, hence my order, which translates to three shots of espresso, with extra steamed, fat-free milk. But good coffee doesn't come cheap. A large cappuccino at the Seattle Coffee Company costs pounds 1.40.

I ask Ally Svenson, the 28-year-old from Seattle who established the company with her husband, to explain the success of these bars. She comments: "when people get very creative with very high quality products, it's a hard adjustment back to not being creative." Cappuccino is no longer enough.

And then there's the convenience. You order a coffee, forgetting that you don't actually have time to drink it, so halfway through you slap the lid on your paper cup, and, as Ms Svenson says, "pick it up and walk off with it. Or, you can start by reading the paper, then go out window shopping, then come back to the coffee." For lifestyle gurus, the permutations are endless. You can have your coffee any way you want, anywhere you want.

This is very different culturally from what you will find in Italy, where an espresso signifies a ritual trip to the local bar, maybe to read the paper, to catch up with the football results, or to put the world to rights.

But what exactly is an espresso, apart from being misunderstood as a powerfully bitter pick-me-up?

Warm and limpid, espresso is a suspension of coffee oils sealed with a hazel-coloured foam, not for sipping or lingering over; down it in one (or two) and then linger and savour its aromas. Aroma is its life; it is not a drink as such, but a means of preparation.

The first espresso machine was exhibited in 1855 at the Paris Fair, where taps were manually operated to control steam pressure. The visions that spring to mind are hair-raising; perhaps you simply placed your order and ducked.

For the serious coffee drinker an espresso is the ultimate experience. It is the richest extraction, and immediacy and freshness are everything: the roasting, the grinding - and the brewing, which takes less than 30 seconds as water at just below boiling point is forced through a wad of finely ground, darkly roasted coffee, under a pressure of nine bars.

One misapprehension about espresso is the caffeine level: it has round about half that of your average instant cuppa, or filter coffee, rather than being the hit most people perceive it to be. An obvious reason is the lower quantity of coffee used in making it, but also that caffeine is a water-soluble substance, and the longer you brew, the more caffeine you extract.

Then there is the issue of bean species. Illycaffe (a cult within a cult), Italy's third largest roaster and the most exclusive commercial brand of espresso coffee, use 100 per cent arabica beans, which means they achieve a caffeine level of less than 1.5 per cent. The robusta bean, which is loaded into instant coffees and favoured for its astringency and low cost, has double the caffeine content of arabica. This is not to say that espresso coffee never contains robusta beans, but as a rule of thumb, high-quality espresso blends do not.

The Italians do have an ESBAD range, albeit modest by comparison to Seattle's: a lungo is a long espresso, a ristretto is very short, caffe is standard, macchiato comes with a drop of warm milk, and a corretto has a little shot of something, usually grappa, to pep it up. They emphatically do not have flavoured syrups.

In London recently, veteran espresso maestro Dr Illy was asked for his thoughts on flavoured syrups. "Many years ago," he replied, "people invented perfume because they didn't smell nice. Goodbye."

Now, if the US is a nation of coffee drinkers, we are tea drinkers; and we have a mug mentality. This is partly climatic; we like a deep pond of brown, milky tea in a vessel large enough to warm our freezing hands. Success for the new US concept may well lie in offering us something we know and love: a milky drink in a mug.

But, however well the Seattle Coffee Company, Starbucks and the like do elsewhere, they will surely be routed at the Italian border. Or maybe not. Stranger things have happened