With crime so increasingly prevalent, there might have been some justification for great severity of punishment, if it had been found by experience that strong repressive measures had invariably been followed by a permanent reduction in the number of criminals; but this is not the lesson that history has taught. It is true that exceptional cases have arisen from time to time in which signal severity meted out to a prominent offender has proved the safest and best course. Prompt and exemplary punishment, even in excess of his deserts, inflicted on a ringleader, has often been the only way to enforce discipline or to prevent the spread of dangerous mutiny; but such cases are rare, and owe their success as deterrents to their rarity, and to the attention that they excite at the time; whereas a consistent course of excessive severity has never been a lasting success, unless combined with powerful preventive measures,[165] and then such a course is no longer necessary. Highway robbery and sheep-stealing were common when they were capital offences, now they are seldom heard of, and the thieving that invariably went on at the foot of the gallows was sufficient proof that the popular belief in the deterrent value of public executions was a popular fallacy.[166] The futile cruelty of the frequency with which capital punishment was inflicted was equalled if not exceeded by the manner in which the secondary punishments were administered. Transportation was introduced[167] in the reign of Charles II., but at first was not, strictly speaking, a legal punishment, but rather an exercise of the royal clemency towards those in "the King's Mercy"; and it may be said to have taken the place in the social scheme of the old system of outlawry which, in former times, enabled a capital felon to save his life by abjuring the realm.