Imagine an army of 20,000 men encamped over seven hundred square miles, with its outposts in every quarter of the globe--an army engaged in never-ceasing warfare with the guerillas of crime and disorder. Imagine something of the work it does. In a city of seven million souls, crammed with incalculable wealth, there are less than a thousand habitual thieves--the exact number is 706--and 161 receivers of stolen goods. In spite of all its temptations, there are but seventeen thousand serious crimes in a year, while the number of more trivial offences is only one hundred and seventy thousand. Few of the perpetrators escape justice. Compare this record with that of any city in the world. Ask Paris, ask New York, ask Petrograd, and you will begin to realise how well protected London is. In a large soft-carpeted room, its big double windows open to catch the breezes that blow from the river, sits the man upon whom the ultimate responsibility for all this devolves, a slim-built, erect man of sixty odd, with moustache once auburn but now grey, grey hair and shrewd hazel eyes--Sir Edward Henry. Imperturbable, quiet-voiced, quiet-mannered, he sits planning the peace of London. He is playing a perpetual game of chess on the great board of the metropolis with twenty thousand men as his pieces against a cosmopolitan fraternity of evil-doers who never rest. He is the one man in the service who must never make a mistake. The Commissioner of the Metropolitan Police sleeps on no bed of roses. He must be as supple as willow, as rigid as steel, must possess the tact of a diplomatist, with the impartiality of a judge. Since the days when Sir Richard Mayne built up the police organisation in its infancy, there has been no Commissioner who so nearly fulfils the ideal of a great police administrator as Sir Edward Henry. Unlike most of his predecessors, practically his whole life has been spent in the study of police science. It is something more than forty years ago since he entered the Indian Civil Service as assistant magistrate collector. He became ultimately Inspector-General of the Bengal Police, and then commissioner of a division. It was there that he first established the finger-print system of identification, as a police device for the registration of habitual criminals which he was to introduce later at Scotland Yard, and which has tightened the meshes round many a criminal who would otherwise have escaped justice. The man in the street knows little of the silent man who is undoubtedly the greatest police organiser in the world. Even on this very matter of finger-prints there is a general confusion with Bertillonage--a totally different thing. The Henry system has practically ousted Bertillonage in every civilised country. If Sir Edward had done nothing but that he would have ranked as one of the greatest reformers in criminal detection. But he has done more--much more.