Being a tour guide in the most visited country in the world should be a pretty good job, buoyed by demand at France's numerous tourist attractions. But, after years of losing professional status, guides are now confronting the 'gig economy'. Online tourism platforms impose freelance instead of salaried work. And in the latest innovation, so-called 'free' tours, the tour guide is not even paid. Cécile Andrzejewski reports.