I do think there is more than a grain of truth in Purnell's less than criticism than Boris using this dual identity to further his undoubted political ambitions by playing the 'dumb blonde' card:
Men generally want to show off how clever they are; clever women are rather good in my experience at fluttering their eyelashes a bit and going, “Oh well, I don't really understand this” and then getting amazing stories [she is referring to journalism]. I think Boris [played] the dumb blond trick in the hope of getting something.
This is a refrain to which Purnell regularly returns, which perhaps explains why the Mayor's PR head was so anxious that a serialisation of this book should not run in the national media that he threatened senior involvement from Downing Street.
This is a well researched biography that will be of interest to watchers of London and UK politics. However, for me it was far too concentrated on 'Boris' and often what read as personal attacks rather than his actual record in office but then, as the parliamentary journalist Quentin Letts explained in talking of his failure as a MP in parliamentary debates (quoted in the book), perhaps that's the way Johnson likes it:
Boris isn't angry. You've got to be angry: you've got to feel things as an MP, but there's no soul, no church in him. No belief. Most people don't just go into politics out of vanity, but maybe he has.
If Letts is right then the fact that he has (and that the British public have allowed him) succeeded is a damning indictment of us all, that is not a party-political point but one of democratic integrity. If. There's not doubt that Purnell would be in agreement with Letts, however.