On Hidden Symmetries in d = 11 Supergravity and Beyond 1

This talk is about hidden symmetries in eleven dimensions, but it is equally a tribute to a scientist and friend, who is eminently visible in four space-time dimensions: François Englert, in whose honor this meeting is being held. Therefore, before entering dans le vif du sujet I would like to express my gratitude for having had the opportunity and privilege to learn from him and to work with him, and for all the fun we have had — involving, amongst other things, dinosaurs within dinosaurs [1] (the ancestor of all modern inflationary theories) and their eleven-dimensional avatars [2], as well as higher states of consciousness [3] and monster strings [4]. These days, many of us who have not yet attained the wisdom that comes with anémeritat, but who share François' enthusiasm 1 Invited talk at the Conference " Fundamental Interactions: From Symmetries to Black Holes " , 24-27 March, Université Libre de Bruxelles, Belgium.