The murder of a policeman in Britain is still a rarity, but on 12th August 1966 the nation was shocked when three were gunned down in West London after stopping a car. Within a few days, two petty criminals John Duddy and John Witney - had been arrested, and the description of a third, Harry Roberts, had been publicised all over the country. But it was not to be for another three months, after one of the largest manhunts known in Britain that Roberts was tracked down in Epping Forest where he had been using his military training to evade capture.