Inside Europe: The skills needed to rebuild Notre Dame

France's President Emmanuel Macron says Notre Dame Cathedral, gutted by fire,will be rebuilt in time for the 2024 Paris Olympics. He can count on master craftsmen called 'companions', whose apprenticeships in carpentry or roof-tiling, for example, stretch back to the men who built Europe's Cathedrals in the Middle Ages. John Laurenson reports from Champs-sur-Marne on keeping the old skills alive.