The problem with legendary figures is that they can be less than fully developed human beings. Take Siegmund Warburg, for instance. According to Niall Ferguson in this substantial and enjoyable biography, Warburg was a visionary and a thinker, the man who invented the hostile takeover, the Eurobond market and the index-linked bond. In short, he saved the City of London as an international financial centre. But he could also be a fickle friend, a bullying employer and an appalling father. He was the type of man whom it was safer to admire from a distance.