Karate gradings for black belt and above are longer and more intensive than those for coloured belts and also require students to pass a short written exam covering first-aid knowledge, nutrition, anatomy and origins of the style. They are held over a weekend once a year in Cornwall or Oxford, and are supervised by the National Coach (Derek Collins, 9th Dan), assisted by other senior grades.
It is a myth that a black belt is an expert! There is a long road ahead yet. Being awarded a black belt simply means that students know the basics and can start to teach whilst keeping far enough ahead of their own students as they progress.