Winston Churchill died at the age of 90 on January 24 1965 and, to commemorate the 50th anniversary of the death of the Tories’ biggest big beast, Mayor of London Boris Johnson has written this entertaining and balanced biography of his hero.

He takes a thematic rather than a chronological approach in jumping around the vast Churchill territory but the ones Johnson has chosen are apt and imaginative and the whole is neatly held together by his chatty prose.

All the usual Churchill factors are there — a glamorous mother, a disappointed father who died young, public school capers and catastrophes, workaholism, prolific journalism and the Nobel Prize for Literature.

Noted for his acid wit, Churchill was politically radical at times, reactionary at others. He had his fair share of military triumphs and disasters — where he displayed courage under fire and the “bulldog spirit” — and, while loyal to some, betrayed others. He loved swimming, champagne, rich food and cigars and, to top it all, sported an endless parade of hats.

Those hats, like his cigars, were a prop in his relentless marketing of the Churchill brand yet the cigars were seldom smoked to the end and his whisky was often heavily watered down, at least in the morning.

It’s a well-researched biography and Johnson has clearly spent a lifetime exploring and reflecting on his man. In the process, he manages to get past the caricature and the myth to assess the complex mixture of virtues and vices that comprised the real Churchill.

He reveals that many of the remarkable stories about Churchill are simply not true, while many others are. He was not a cad, neither was he a god. But, so Johnson the classicist insists, he certainly had megalopsychia, greatness of soul. “His ethic was really pre-Christian, even Homeric.”

Churchill was not particularly “Tory,” viewing himself as above party politics. He used the Tories to become an MP, defected to the Liberals as their fortunes rose then returned to the Tories when Liberal fortunes declined. “Anyone can rat, but it takes a certain amount of ingenuity to re-rat,” Johnson remarks.

Like most successful people, Churchill was an opportunist and a chancer. This made him enemies, particularly within the Tory Party, where many were furious when he became prime minister. As the author notes, young Tories who put up the iconic pin-stripe and machine gun poster and sport a polka-dot dicky bow ought to remember that.

Yet Churchill was not a Conservative outsider in the way that Margaret Thatcher was. He was, after all, an aristocrat — not merely posh but ducal. He despised Soviet communism as much as nazism or anything that threatened to suppress the eccentric individual.

He certainly had no socialist leanings — he had Liverpool dockers fired upon in 1911 — but particularly during his liberal phase he was an effective social reformer and, along with Lloyd George, helped introduce labour exchanges, unemployment benefits and tea breaks.

Subtitled “How one man made history,” Johnson’s work makes a good case for the view that exceptional, well-placed individuals can alter the course of history. History is not entirely determined by economic forces, as some Marxist historians would have it. People, as Jean-Paul Sartre argues in his Critique of Dialectic Reason, make history by choosing their response to their situation.

Without Churchill’s pre-war warnings about the dangers of appeasement and pacifism in face of German rearmament, Britain would not have resisted nazism long enough for him to become the great war leader he undoubtedly was.

All this and more is there in Johnson’s book, which reveals an acute brain beneath those blond locks.

Gary Cox’s The God Confusion: Why Nobody Knows the Answer to the Ultimate Question is published by Bloomsbury. Twitter @garycox01