Last week a restaurant in London decided to run a month-long "pay what you want" deal. You go, you eat, you drink, and then you pay what you think it was worth. It sounds like the first step towards financial ruin - in a recession, surely you can't bank on public generosity? Well, perhaps it's not as economically disastrous as it sounds. In Berlin, a similar system has been running for more than 10 years - and business is thriving.

The Berlin Weinerei are the inadvertent brainchild of Jürgen Stumpf, who moved to the city in 1996 from the Bavarian town of Franken, where his family owns a five-hectare vineyard. He opened up a small wine shop selling his family's wares in the rapidly emerging east of the city, and invited his nextdoor neighbour, Argentinean immigrant Mariano Goni, to cook for guests on Thursday nights. They didn't know what to charge people, and so left it to their customers' discretion, asking them to leave money in a box at the front of the shop.

Locals began to flock to the shop, and it became the talk of the town. Today, there are three different Weinerei owned by Stumpf and Goni, all within walking distance of the Zionskirchplatz in southern Prenzlauer Berg, an area in the former east, where cheap rents in turn-of-the-century apartment blocks have attracted hordes of young artists and creative enteprises over the past two decades.

Of the three, Perlin is the most intimate of the venues - a small bar lit with candles. When I visited on a freezing evening in January, there were 20 people seated around patterned banquettes and tables with French chanson music wafting from the speakers.

There was a bar, of sorts, but it was really just a table laden with bottles of wine. And behind it there was a sommelier, of sorts. "You want wine? Take wine. You hungry? I cook for you." As I fumbled with the top of a bottle of chilled Reisling, I was stopped in my tracks. "Ah!" shouts the sommelier, pointing towards a ceramic gargoyle balanced on the table "One euro please." I rolled a coin into the gargoyle's mouth, poured myself a glass, and retreated to the sofas. The idea is that you rent a glass and then help yourself to as many refills as you want.

The bars aren't pay-as-you-like all of the time - just after 8pm. My next drop was a Spanish Tempranillo, then a glass of the house red from Franken, and then a Bavarian prosecco. Co-owner Mariano Goni was in the kitchen, cooking up turkey fillets and pumpkin mash. I had some of that, too.

On the table next to me, three female students were drunk and giggling. They'd been on the homemade schnapps, which resides in bottles with peeling hand-written labels above the bar. On another table, another group were sharing a bottle of something fizzy. The staff, without a huge amount to do, were wobbling about the place joking with regulars. I asked the students how much they were going to pay. "Well, we've had four glasses of wine and some food, and normally we'd pay about ?20 for that, so that's what we will pay," hiccupped one. "We love this place, so it wouldn't be fair if we took the piss."

Despite the arguable naivety of the Weinerei's business plan, they have an ace in their pack. Mariano is an outrageous flirt. When delivering the students' meals, he promised one that he would take her to Argentina where they would spend two years exploring the country on horseback. In the end, the girls paid ?25 each.

But surely not everyone is as generous. "No, sometimes there are assholes who spend the entire night here and pay ?5," said Mariano. "Especially Spanish people. We should have a monument dedicated to us in Madrid, they owe us so much money! But no, it's OK. Most people are very generous. We won't get rich doing this, but we never intended to."

As I left, 25 of my euros were deposited in a large vase by the door, where they joined a respectable wad of other people's offerings. "Thank you," yelled Mariano, his arm curving the air with a flick, "We love you very, very much!

Note to those trying to recession-proof their businesses in these tricky financial times: you could do a lot worse than charming your way through it.

Getting there

? weinerei.com: The three bars are Perlin (Griebenowstrasse 5, +49 30 657 06756), Fra Rosa (Zionskirchstrasse 40, +49 30 4069 0951) and Forum (Fehrbelliner Strasse 57, +49 30 600 53027).

? British Airways flies Heathrow-Berlin from £110 rtn inc tax, bookable until 28 March.

? The Circus Hotel (+30 2000 3939) has doubles from ?75 per night B&B