The American gospel singer Dee Dee Bridgewater was belting out Oh Happy Day, the signal that the "Popemobile" had reached the esplanade beneath the Eiffel Tower. The crowd attending the 12th World Youth Days danced and sang to the music: the French newspapers are calling the festival "the Catholic Woodstock".
Then I spied the Irish tricolour in the sea of half a million people. Alex Barniville (16) from Donnybrook in Dublin, sat on the shoulders of Liam McCormick (18), from Clontarf.
Alex waved the tricolour to the rhythm of Dee Dee Bridgewater. "The Pope is King!" he kept proclaiming as the Pontiff advanced through the cheering crowd. Thomas Bridge (22), from Bray, stepped forward when I asked the Irish pilgrims why they had made the journey to Paris. "First of all for an encounter with Christ," Mr Bridge, who works for an engineering firm, said. "Second, to meet other young Catholics from Ireland and around the world. And I wanted to have a good time."
Pilgrims from the South Pacific, Italy, Korea and the US also said they came to meet like-minded youths. Unlike the other foreigners, the Irish didn't think today's youth were in crisis.
But there was one problem, Mr McCormick said: "Being a Catholic is considered uncool these days in Ireland."
French participants thought Pope John Paul II was too conservative on birth control, divorce and abortion. "Absolutely not," Sean Ascough (31), from Blessington, Co Wicklow, said. "He's the best Pope we've ever had. He's got real wisdom. When people follow the teachings of the Church they are happy."
When the Saints Go Marching In boomed over the loudspeakers, and the whooping and dancing recommenced. "People think Catholics are boring," John Byrne (17), from Loughlinstown, said. "This proves we're not. It's really reassuring to know there are other people like us - that it's all right to be Catholic."
Father Kevin Doherty (33), from Bray, said Catholics in Ireland "don't have the spirit". At the Paris festival, they had discovered it. "Tell them it's great fun - and there's not a collection box in sight!"
