Years before flames ravaged Notre-Dame Cathedral, the landmark’s custodians realized they had a problem.

In 2013, the cathedral hired Didier Dupuy and his son to scale the building and install lightning rods at different points, including its central spire. Gaping holes and cracks they discovered in the lead roofing shocked them. Just below was a dry and dusty space of timber beams, known as “the forest,” that had supported Notre-Dame’s roof for centuries. A job that was supposed to last a couple of weeks took three months as the duo performed emergency repairs before quitting in frustration.

“We told them, you need professionals for this. We can weld, but it’s not pretty,” said Mr Dupuy, who removed 110 pounds of rust from the cross atop the spire. “The cross was in very bad shape.” Notre-Dame’s forest caught fire, incinerating the central spire and most of the cathedral’s roof in a disaster that dismayed the world.