One of the first ever dinosaurs to be discovered was discovered - in part on the South Downs! The decade was the 1820's, the man was Gideon Mantell and the dinosaur was the Iguanodon.
Obviously, the South Downs are quite extensive and parts were underwater during the age of the dinosaur, so we'll never truly know if you're standing where a dinosaur once stood, but we'll presume so, for the sake of the cache!
What follows is a quick 'artist's' impression of how the South Downs may have looked all those years ago. (Sepia added for fake nostalgia).
Happy stamping!
As an aside, I once made an animation involving dinosaurs, it's a bit strange, but if you feel like watching it you can do so here: Crazy Dinosaur Movie