Down at Westminster Pier, where the river cruisers come and go in the unusually hot August sunshine, a chatter of languages floats ashore on a merciful breeze. French, Arabic, Hindi, Russian, Spanish. Tourism, it seems, is alive once more.
But one tongue is barely heard. That instantly recognizable American accent, usually so audible in tourist spots around European capitals, is all but silent. It's not that the US contingent is unusually quiet. It's that it is barely present.
"My son was just saying how few Americans there seem to be," says a rare visitor from across the Atlantic, Jodell Scott, as she and her family ponder their next move after a Thames cruise.
"The war situation has made a lot of Americans afraid to travel," she adds. "We talked about it and thought, 'We can't be afraid.' We'd planned this trip a long time."
After two dismal years for tourism in Europe, visitors are starting to come out of their shells again. A succession of events unsympathetic to tourism - Sept. 11, the global economic downturn, the Iraq war, and the SARS virus - put millions off travel until very recently.
That trend is starting to turn around now, however, with some European countries like Britain and Spain reporting growth in visitor numbers. The World Tourism Organization reported in June that the tide could be about to turn. "Prospects for Europe show a notable improvement," it said.
But no one has yet managed to lure back the high-rollers of the tourism industry - the Americans. Some have stayed away due to war and terrorism concerns; others have adopted an "America first" patriotic approach to vacationing; still others are deterred by the weak dollar, which makes foreign holidays more expensive.
In Britain - the most popular destination for American tourists to Europe - figures for the first half of 2003 show an 11 percent decline in US visitors. In Italy, it's more than 20 percent, while in France, it's even worse: an estimated 26 percent drop this year.
"Until Sept. 11, about 45 percent of our clients were Americans," laments Mauricio Mistarz, head receptionist at a small three-star hotel on the Left Bank in Paris. "Now, on a good day, Americans fill 20 percent of our rooms."
The protracted slump in US visitors to Europe is alarming for the millions of Europeans who profit from their dollars - from the travel agent to the taxi driver, the postcard vendor to the tour guide.
American visitors tend to stay longer and spend more than any other tourists. In France last year, the Americans spent more than British and Irish visitors combined, despite being outnumbered 5 to 1. In Britain, the average American spends $1,000 a trip, far outstripping European visitors.
All of this means that US reluctance to travel costs European tourism dear.
The French hotel group Accor reported a 7.8 percent slump in first-half revenues; Italy's tourist authority reported multimillion losses for hotels in the first half of this year.
"Americans are crucial to tourism in the UK," says Neil Wootton, managing director of the British travel firm Premium Tours. "They bring in more tourist revenue than any other nation in the world. They are far more likely to go out, go on tours, buy souvenirs, go to the theater."
Mr. Wootton says that before the Iraq war, Americans made up around a fifth of the traffic on board his coaches visiting British heritage sites such as Stonehenge and Leeds Castle. Now, "we are taking more passengers overall, but very, very few Americans," he says.
The dearth of Americans In Italy is obvious not just to those in the tourism industry. In Pisa, home of the famous tower, police officer Giacomo Grasci says he hasn't seen so few Americans since the 1991 Gulf War. "I think they are afraid of flying because of Iraq and because of the threats against them," he says. "We are seeing the same number of Germans, French and tourists from other parts of Europe, but visitors from the United States, South America and Japan are way off."
The bitter row between the US and France over the Iraq war may have decimated the ranks of camera-toting Americans in Paris and elsewhere in the country.
Marie-Caroline Laforgue, who works at the Hotel de France, across from Versailles, recalls how one American client recently asked her whether she should say she was Canadian to avoid hostility. "I just laughed," she says. "It's true we disagreed over the war in Iraq, but they don't risk anything here."
Ms. Laforgue says, however, that she has more US guests than in the past. She says the Americans tell her they feel safer staying on the outskirts of Paris.
In truth, this has not been the best year for visiting Europe. Forest fires have ravaged swaths of Portugal and the Riviera; a heat wave in Paris has led to deaths; a strike by French thespians has robbed the country of its much-loved summer festivals; and excessive heat on the Mediterranean has sent many scurrying for cover.
Another factor discouraging Americans has been the strength of the euro and sterling. Just two years ago, a dollar bought €1.20; now it buys less than 90 cents. That makes a European vacation more than 30 percent more expensive for Americans.
So what can Europe do to woo back its favorite visitor?
France recently launched a $2 million marketing blitz under the seductive slogan "Let's Fall in Love Again." Britain is unleashing a $3 million US television advertising campaign promoting history and heritage. Airlines and hotels are offering fresh package deals with deep discounts to get the American market on the move again.
But they will have to vie with US domestic alternatives offering "patriotic" holidays, as well as other Western Hemisphere options perceived as safer than flying across the Atlantic.
"There is increasing competition from domestic and shorter-haul destinations," says Elliott Frisby of the VisitBritain tourist authority, adding: "Americans are prepared to travel if the price is right and the quality is right.
"They are nervous travelers, but we are working very hard to reassure them."
• Terrence Murray in Paris and Cheryl Heckler in Pisa contributed to this report.