Has clamping down on drugs made the Tour de France slower?

The Tour de France, we are told, has finally cleaned up its act and clamped down on the use of performance-enhancing drugs. But if it has, should we expect today’s drug-free riders to be slower than their drug-fuelled forebears? Can statistics tell us whether the Tour de France really is cleaner than it was? Also in the programme: does when you retire influence when you die?