In considering this subject we should first briefly examine how guided missiles came on to the scene. Manned flight in heavier-than-air vehicles is some 50 years old and, once the early scepticism of sopie critics had been overcome, very large and highly successful efforts were made to use flying machines of this kind for direct military purposes. The scope of these efforts and the measure of success that attended them are well known and have been the subject of many of the papers and much of the discussion which the Royal Aeronautical Society has enjoyed in the past 50 years or so of its 90 years of active life. It is indeed significant that the two World Wars of the past 40 years have, by reason of the extra effort they focused on military aviation, been the cause of most of the advances in aviation and thus brought about commercially and economically successful civil aviation as we have it today.