David Cannadine reflects on the merits of youth and age in our political leaders and finds the current set taking their parties into next week's election strikingly young. "It's a curious and unexplained paradox that in earlier times, when life expectancy was much lower than it is today, politicians were generally much older; whereas nowadays, when life expectancy is much greater, it's widely believed, at least in some quarters, that politicians ought to be younger". Producer: Sheila Cook.