Under the English Channel ? After three years of sweat and toil, Philippe Cozette tunneled into history one wintry day in 1990, using a compressed air drill to power through the last chunk of chalk marl separating undersea tubes extending from the shores of Calais in France to the white cliffs of Dover in England.

When the Frenchman reached through the hole to shake hands with his English colleague Robert Graham Fagg on the other side, the two countries were physically linked for the first time since the last Ice Age.

“Welcome to France,” Cozette said in English. “Bonjour, mon ami,” responded Fagg, before exclaiming in a distinctly English accent: “Vive la France!”

The Channel Tunnel — or Chunnel as it’s affectionately known — opened four years later on May 6, 1994. The world’s longest undersea passageway stands on its 15th anniversary as a dazzling engineering feat that is finally turning a profit following years of crippling losses — and, while tucked away out of sight, it has become a monument to the possibility of change: After centuries of rivalry and warfare, France and England have become partners in a successful enterprise that has changed the face of Europe.

“We don’t have the same way of doing things, but little by little we got to understand each other,” Cozette said, talking about the French and English work crews — but making an observation that could very well apply to the two countries as well.

Cozette is proud of the tunnel, an accomplishment he dreamed of when he was growing up in Calais, the French terminus, and looked toward the English coast some 20 miles away.

“When I look at the white cliffs of Dover, I think of the tunnel underneath,” Cozette said.