‘Don’t talk too much. Listen instead. Don’t ever appear surprised; it looks provincial. Don’t reveal your ignorance by asking for explanations. You can learn a thousand things without anyone realising you didn’t know them already.’ These words of advice were uttered by Madame de Maintenon, mistress and eventually morganatic wife of King Louis XIV of France, to one of her protégées at Saint-Cyr, the school she founded for impoverished young noblewomen. But they might also come in useful for a certain type of contemporary biographer.