Not that he is ever dull when reaching into the more distant past. Few will forget his description of Edward Gibbon, with his big flapping cheeks, 4ft 8in body, bright ginger hair and – a detail I would have preferred not to know – permanently distended scrotum. Cohen has a magpie’s eye for entertaining facts: we learn, for example, that the Mongols ranked historians lower than prostitutes, and that the 9th-century chronicler al-Baladhuri ate such large quantities of a memory-enhancing nut that it drove him mad. (“Superfood” consumers beware.)

One of Cohen’s themes is that in order to understand a historian, we must see him or her as a rounded, flesh-and-blood human being. This principle may help to justify the vivid descriptions of individual lives here; but in some cases (eg Machiavelli, Trotsky) we go through many pages of their personal adventures to arrive at terribly brief accounts of their actual historical writing. 

Lady Mary Wortley Montagu, who was not a historian but wrote colourful letters from Istanbul, gets in; Catharine Macaulay, who led a ­relatively dull life but was one of the most important 18th-century historians, is not even mentioned.

Another theme, inevitably, is the modern debate about whether historical writing can be “objective”. This is linked to the previous theme, as we are all creatures of our society and our personal experience; and Cohen writes sensitively about this in a marvellous chapter about Dom David Knowles, the great historian of monasticism who had literally gone awol from his own monastery in order to live with the woman he loved.

Writing with a conscious agenda to distort the truth is obviously wrong (and no one would accuse Knowles of that). But the big question, not really answered here, is how people can know that they are being more objective rather than less, in a modern world where pure objectivity has been declared impossible. Most would agree, at least, that the effort is worth making. But perhaps not all. When Cohen asked the Marxist Eric Hobs­bawm if a historian could be objective, he laughed and said: “Of course not – but I try to obey the rules.” That sounds like a less than wholehearted commitment.