Boris Johnson is something of a phenomenon; easily the most popular politician in Britain (outside Liverpool and perhaps Bethnal Green), he has become a wildly popular and hugely marketable brand in his own right. Therefore, it is only natural that towards Christmas time, when hardback books of a certain sort begin their descent toward the bookshelves, one about Boris Johnson should be among them. Boris’s own effort for this year’s Christmas market (I say ‘effort’ - it is another repackaging of various previously published Telegraph comment pieces, and therefore no effort at all) is already in the shops. But, as with any popular brand, others always want to cash in on the action, and so we find ourselves presented with the first biography of Bo-Jo.

To be fair to Andrew Gimson, this is more a matter of the great man sharing his great good fortune bountifully amongst his friends. Gimson is well placed to write a biography of Johnson, being as he is a colleague at the Telegraph, sometime ‘foreign editor’ of the Spectator under Johnson (although he recalls never once leaving the country in service of this unpaid position), and a personal friend. Of course, these qualifications do also spell out the sort of picture with which Gimson is liable to furnish us; it would be fanciful in the extreme to suggest that this biography is a hatchet job.

At the outset one presumes hagiography, but it’s much better than that - Gimson has constructed a near-flawless page-turner of no small distinction, with a genuinely impressive amount of interviews and research behind it. What is remarkable is how much energy he manages to inject into the telling. Once the book hits its stride - after some interesting detail about the Johnson forefathers in Turkey, and a short account of the Bo-Jo childhood (oddly reminiscent of John Lanchester’s The Debt To Pleasure - with the narrator stalking his subject’s old stamping grounds) - it is more like whipping through a deftly plotted collection of well-turned anecdotes than wading through a political biography.

The majority of the audience for a biography of Bo-Jo will already be well acquainted with the basic facts: the Eton education; the Oxford Union presidency; the brief early marriage to Tatler cover girl Allegra Mostyn-Owen; the dismissal from the Times; the spell as Brussels correspondent for the Daily Telegraph; the marriage to ‘lefty’ lawyer Marina Wheeler; the editorship of the Spectator; the successful election to parliament as MP for Henley; the now legendary Have I Got New For You? appearances; the affair with Petronella Wyatt; the infamous Spectator attack on Liverpool’s ‘grief culture’... the list goes on.

Each chapter in the Johnson history seems to have been lived with a view to a perfect story arc - from tentative beginning to glorious triumph. At times the note of hagiography does loom a little large, but this too is all part of Gimson’s wider scheme. He opens his introduction with a quote from Gibbon concerning his decision to essay the Decline and Fall of the Roman Empire, and while Gimson has subtitled this biography ‘The Rise…’ it would have been more accurate to have left in the heavily implied ‘Fall’.

For much of the book it seems like the biography represents the first building block in a campaign toward party leadership. In an early conversation when the project is first mooted (before the ‘scandals’ broke), Gimson argued: ‘painful episodes in Boris’ past would lose their power to hurt him once they were known, and it would be much less dangerous to deal with this stuff now than when he became Prime Minister’ (my italics). Throughout the book, mentions of the Prime Ministership occur with increasing frequency. It does appear that Boris and Gimson, if no one else in the country, really did regard this as a serious proposition for quite some time. And it is this sense of where Bo-Jo could have been heading which makes the final chapters, where the whole precarious edifice seems to come crashing down around his hapless head, so dramatic.

What is fascinating is, for a political biography, how little it deals in policies or indeed politics. The author quotes an early conversation with (former Telegraph and Spectator editor, currently engaged on writing Thatcher’s official biography) Charles Moore who, on hearing that Gimson is to write a biography of Boris, advises ‘you’ll need 200 pages for his foreign policy.’ As it is, the whole book weighs in at 263 pages; not one of them, according to the index, concerning foreign policy. Of course there is some discussion of Johnson’s politics, but it is kept at a very general level; quite possibly, one suspects, to avoid alienating the significant proportion of the Boris fanbase who either care not one jot about his policies, or enjoy Boris-the-personality in spite of them. Instead of politics we are given portraits of Boris the Quixotic; Boris the Lazy; Boris the Reckless, Boris the Heroic and eventually, by the end, Boris the Unsure. While Gimson is excellent on the storytelling aspect, he is less sound on this more speculative, psychological side of things. Like his subject, he tends to display a rather English horror of really getting to grips with, um, feelings and all that. So the few insights which he does attempt are slightly tentative and awkward (‘People love him because he makes them laugh, but also because they glimpse the hurt young kid behind the laughter.’).

As the book gallops toward its conclusion, it often feels as if written more as a diary concurrent to the unfolding of the events detailed. The book was conceived in 2004, quite possibly as a plank in the future campaign by Johnson for the leadership of the Conservative Party; the earlier chapters concentrate on Bo-Jo’s huge promise and potential. Within a year, Boris had lost his seat in Cabinet, had an affair exposed by a Sunday tabloid and was on the way to resigning his editorship of the Spectator. The last two years, in which he was overtaken by near-contemporary Old-Etonian David Cameron in the race for the leadership, when the book was written, have scarcely been its subject’s happiest. It seems a shame that Gimson has gone ahead and published the book now, with such a downbeat ending. He may think this is the beginning of the end of Johnson. Alternatively, he may have simply wanted to catch the Christmas market. Either way, as it stands, irrespective of its conclusion, this is still a rollicking good read - a classic Boy’s Own adventure, and hopefully, a second edition, or volume, will have a rather happier conclusion.