‘When I was 14, my father was so ignorant I could hardly stand to have him around,’ wrote Mark Twain, ‘but when I got to be 21, I was astonished at how much the old boy had learned in seven years.’ Evidence, perhaps, that notwithstanding his then progressive stand on abolition, imperialism and women’s suffrage, a centenarian Twain might have agreed with Winston Churchill that, ‘If a man is not a socialist by the time he is 20 he has no heart, and if he is not a conservative by the time he is 40 he has no brain’.