Before Tik Tok and Google Reviews, there was the Michelin Guide. First published 125 years ago, the guide encouraged drivers to wear out their tyres by visiting the best restaurants in France, as judged by the guide's mysterious inspectors. The inspectors' identities are still a closely guarded secret, but the new documentary series Knife Edge: Chasing Michelin Stars offers rare insight into their process and access to the kitchens of top chefs gunning for those elusive stars.