It reads at times like a mixture of Monty Python and the Horrible Histories. He describes the French generals during the Second World War as “white-haired dodderers in their Clouseau-like kepis” commanding “an origami army”. Hitler and Himmler are part of a “demented crew” with “deranged plans” for a new world capital called Germania. “At its heart was to be the Hall of the People – a demented granite version of the Pantheon of Agrippa.”

Meanwhile, our great wartime leader, according to Johnson, spent the war dressed in “strange Victorian/Edwardian garb”, giving the appearance of “some burly and hung-over butler from the set of Downton Abbey”.

At one point Johnson deliberately invokes one of Monty Python’s more iconic images as he ponders how British fortunes may have fared during the war without Churchill at the helm. “Let’s send down one of those giant Monty Python hands,” he postulates, “and pluck him [Churchill] from the smoke-filled room. Let us suppose that he’d copped it as a young man, on one of those occasions when he had set out so boisterously to cheat death.”

Nor is the author shy about placing himself centre stage in the narrative. He writes about visiting Chartwell, Churchill’s family home in Kent, in an attempt to better understand the “teeming brain that helped invent the tank and the seaplane and which foresaw the atom bomb”.

Johnson’s novel conclusion is that the entire house has been constructed as “a gigantic engine for the generation of text”, enabling Churchill, who was to become the recipient of the Nobel Prize for Literature in 1953, to produce more words than Shakespeare and Dickens combined.

In another classic Johnsonian diversion, he sets off on his bicycle in the rain along the Romford Road in east London to visit the grave of Churchill’s beloved nanny, Mrs Everest. “I am soaked. My blue suit is black and shiny with water and there is a sucking noise in my shoes as I get off my bike.” As with the many other visits Johnson undertakes in the course of the narrative, there is a more serious purpose underlying his humorous antics.

The gravestone Churchill and his brother Jack erected to Mrs Everest’s memory is testimony to Churchill’s deep humanity.

Indeed, as with so much Johnson does in his public endeavours, there is a profound point underscoring all the levity and bravura. As the title suggests, the book is an exploration of the many distinctive facets of Churchill’s character that made him the man he was, and provided him with the inner strength and spirit that enabled him to save the British nation in its darkest hour.

While Johnson is clearly an admirer of Churchill, it can be difficult to see what new insights he brings to the study of the statesman. The obvious subtext, of course, is that Johnson is seeking to compare his own reputation as a political maverick with that of Churchill, which poses the question: what would Winston Churchill have made of Boris Johnson?

Boris Johnson will be taking part in a Q&A with Gaby Wood on October 23 at Imperial College London. Tickets are £40 (including a signed copy of The Churchill Factor) and are available from telegraph.co.uk/borisjohnson.

The Churchill Factor by Boris Johnson

416pp, Hodder, Telegraph offer price: £20 (PLUS £1.95 p&p) (RRP £25, ebook £8.96). Call 0844 871 1515 or see books.telegraph.co.uk