The penthouse restaurant, with picture windows overlooking the Seine and Notre Dame, has long been a favourite with presidents, royalty, wealthy tourists and well-heeled Parisians.
"I am very sad," said Claude Terrail, owner and director of La Tour for 50 years. "But my team and I intend to do everything in our power to recover that star."
The Michelin Guide famously refuses to discuss the reasons for demoting a restaurant in this way. Mr Terrail insists, however, that he has no plans to fire Manuel Martinez, the chef he headhunted from the Ritz.
He remembers another annus horribilis in 1952 - the last time he lost his third star. "We won it back in 1953," he said.
"Tradition is what La Tour d'Argent represents. People come to propose marriage, to celebrate, for a once-in-a-lifetime experience of rich French heritage. Now they come through the tunnel by Eurostar and return to England after lunch."
The restaurant, noted especially for its "canard au sang" (bloody duck), is booked for days in advance; the first available table yesterday was on Monday week. If you resist the more expensive bottles among the 500,000 in its cellars, you can eat well for around 875 francs (pounds 113) a head. This does not include aperitifs and coffee, or tips to the parking valet, two doormen, page who leads guests to the lifts, two lift operators, two restaurant greeters, maitre d'hotel or anyone else who appears on the scene.
Mr Terrail says he will improve his cuisine but says he will never strike the classic dishes from his menu to appeal to modern gastronomic fashions. "The great dishes of the world are made according to very precise recipes and require neither reform nor inspiration," he said. "At La Tour d'Argent, the client is king. Finally, it is he who awards the stars."
n There are 35 Michelin three-star restaurants in Europe. France has 19; Britain has four.Reuse content