The Rue du Bac is an unlikely place for the opulence of Paris to collide with the poverty of eastern Europe.
President Jacques Chirac's daughter lives in the street. It boasts two sites of Catholic pilgrimage: the chapel of the Epiphany and the chapel of Our Lady of the Miraculous Medal.
Combined with the Hediard delicatessen and the capital's most expensive department store, Le Bon Marché, they attract a constant flow of affluent foreigners and Parisians.
Since the late 1990s, the 100- metre stretch has also attracted a large number of beggars from eastern Europe.
"They're all Romanians," says an Italian nun from the Daughters of Charity of Saint Vincent de Paul, who look after the Chapel of the Miraculous Medal.
"Sometimes there are dozens of them around the door. We no longer let them in the chapel, because they were begging inside. The children are exploited by the grown-ups, so giving to them is not charity. When the police come, they vanish."
A few stocky security guards wearing suits and ties are all that separate these hungry immigrants - their cardboard signs all say they are hungry - from the new Chanel boutique inside the Bon Marché and the champagne, caviar and foie gras in the Grande Épicerie.
"We can keep them out of the store and protect the windows," one guard says. "The begging and pick-pocketing are the police's problem."
There are gendarmes a-plenty outside the Prime Minister's office two blocks away, but I've never seen one in this part of the Rue du Bac.
Some residents now circumvent the street to avoid the urchins who accost them. When my bicycle - which I had chained to a signpost - disappeared during a five-minute errand last week, my concierge said: "You should have known better than to leave it there!"
My optician lost her wallet filled with cash and credit cards in the same place.
I notice several beggars glancing towards a young man in a grimy tracksuit and conclude he is the leader.
Marius pretends to sell a newspaper called SANS-LOGIS (homeless), but he covers the badge pinned to his sweatshirt when I approach, then gives a different family name from the one I read.
In broken French, he tells me he is 24 years old, from Bucharest, and that he sleeps in a park at Saint-Denis, north of Paris, with a dozen Romanians and Poles.
"The police don't bother me. The police know I don't steal," he says.
"In Romania, I don't have the right to be a gypsy," Marius continues. "They say we are Indians. I have no right to enter a church in Romania. Here, this neighbourhood, a lot of gypsies."
Marius's demands for money grow more insistent. Then he grabs my notebook and tries to tear out the pages.
When I go through the motion of reporting my stolen bicycle to the local commissariat, there are a dozen interpreters' business cards tacked to the bulletin board - all Romanian, Moldavian and Polish speakers.
"Most of the petty theft in Paris - bicycles, parking metres - it's all east European," the officer explains. Yet Romanians rank 11th - far behind Albanians, Russians and Ukrainians - in European crime statistics.
In recent months, French police have dismantled several Romanian mafia rings which prostituted children or forced cripples to beg.
Libération sent a correspondent to Buzescu, south-west of Bucharest, where the mafia bosses are building Disneyland-style palaces. They charge handicapped Romanians, many of them gypsies, €500 to bring them to France, where the traffickers' victims are allowed to keep only €5 of each day's earnings.
Since January 2002, Romanians no longer need visas to enter countries which are party to the Schengen agreement. In Brussels, France has discreetly broached the possibility of reinstating a visa requirement for Romanians.
It would be a devastating blow to a country that has great hope riding on its application for EU membership. "It's in our interest to show Brussels that we can control our borders, which will become the most eastern borders of the Union after we become a member," the Romanian Prime Minister, Mr Adrian Nastase, told Le Monde.
The begging mafia constitute "a very serious problem for the image of Romania", he admitted.
For the first time, the French government is addressing the problem. The Interior Minister, Mr Nicolas Sarkozy, received his Romanian counterpart in Paris last week and four Romanian police officers have been dispatched to help their French colleagues.
Mr Sarkozy will sign a co-operation agreement in Bucharest on August 30th.
In the meantime, the beggars are still hard at work in the Rue du Bac.