Balzac, in his novel The Splendors and Miseries of Courtesans, described him as the "most powerful person in France". To the French detective novel or cop flicks the juge d'instruction is an essential character. Simenon's Inspector Maigret relied on these examining magistrates to provide the necessary stupidity to enable him to demonstrate his astuteness. But the job - created by the Napoleonic code more than 200 years ago - is to be abolished. It is Nicolas Sarkozy's wish, and last Friday an of