For many, the British policeman is still the ' friendly bobby.' His image is envied by his counterparts abroad. But the policeman has little to be jolly about today. Police are harder-pressed than at any time since their creation a century and a half ago. Of the 1.500,000 indictable offences committed in Britain last year, more than half were never cleared up. We demand more of our police but complain when they seem too efficient. The policeman's world grows harsher. Can he hope to outlive these changes? Written and narrated by Paul Ferris Produced by MICHAEL WEIGALL (The thinning blue line: page 5)