The saviour of The Times and serial defender of the empire

Even at the classy end of the market, publishers' claims are rarely notable for restraint. But the copywriter responsible for the dust-jacket of this book has managed it with the note of qualification in the description of Alfred Harmsworth, Viscount Northcliffe as "arguably the greatest of the press magnates". In Britain, at least, he has no real challenger.

Northcliffe did not invent the British popular press. But the greatest rewards rarely go to the truly original. Instead, as Matthew Engel has pointed out, Northcliffe was the first to find the formula for real long-term success with the Daily Mail, which he started in 1896. Thirty when the Mail was launched, he was already a proprietor of consequence, founder of the hugely successful magazine Answers and owner of the London Evening News.

He went on from this to found the Daily Mirror, briefly own The Observer and rescue The Times from possibly the deepest hole in its somewhat chequered history. His empire also incorporated numerous magazines and local papers.

In spite of having no children of his own, he was the most successful dynast among British press barons; the Harmsworth clan controls the Daily Mail to this day. J. Lee Thompson also notes in passing (though without any reference to its longer-term significance) Northcliffe's financial assistance to the Australian journalist Keith Murdoch when he started buying newspapers.

During the first world war Northcliffe was widely credited/ blamed for the downfall of Herbert Asquith as prime minister, while his work as a British representative in the United States helped maintain the loans that paid for the war effort.

This Citizen Kane-like trajectory reached a suitably dramatic conclusion. Long diagnosed by his critics with the occupational malady of press barons, megalomania, he went genuinely off his head and died at 57.

So vastly active a life sets the biographer serious problems, not least of scale. The newspapers by themselves could furnish years of reading, even before personal papers and correspondence are thrown into the equation. When your subject inspires extremes both of sycophancy and of fear and loathing, there are serious challenges of judgement in weighing the validity of contemporary accounts.

Thompson has dealt with the problems of scale by focusing his volume specifically on Northcliffe's political involvements. This includes his one highly unsuccessful venture into electoral politics as Conservative candidate for Portsmouth in 1895, failing in a winnable seat in a good year. It is hard to escape the conclusion that Northcliffe was uncomfortable in arenas where he was likely to be challenged directly and without deference - he rarely attended or spoke in the House of Lords and during a libel action between Lever Brothers and the Mail took ignoble refuge in France. Politics is defined in the "high sense", in Northcliffe's direct dealings with the political elite and the pronouncements of his papers, rather than looking at their place in the broader politico-media culture of the time.

These themes are covered in scrupulous, exhaustive detail. For anyone wishing to know where Northcliffe was, or what he was doing, in just about any month between his purchase of the Evening News in August 1894 and his death 28 years later, this book will be hard to beat.

Consistent themes do emerge from a largely straight-line narrative - a fascination with travel and its technology, which ran through enthusiasm for bicycles, cars and flight, and a populist nationalism that expressed itself through a concern for empire and a preoccupation with military threats to Britain. Mock histories of invasions brought on by failure to arm sufficiently were a recurrent theme in Northcliffe's newspapers, starting with the French invasion envisaged in a Portsmouth paper in 1895. The enemy later changed, but the genre did not.

The book is billed as "the first objective assessment of both the private figure and the public man". Thompson certainly strives for balance, while sharing most biographers' tendency to give his subject the benefit of the doubt. But his Northcliffe is a peculiarly bloodless figure, the nuances of a formidable personality rarely glimpsed. And assessment is in short supply amid the mass of narrative.

Northcliffe and the Mail tend to be treated as indivisible - the popular daily's leader articles treated as direct expressions of its master's will and beliefs. There is little sense of the interplay and debate that take place between editors and even the most dominant proprietor, or of the extent to which Mail policies may have reflected commercial imperatives as much as Northcliffe's political outlook. These issues, perhaps because of the quality of The Times archives, are better reflected in the treatment of that paper.

Precisely how much political influence a newspaper wields, and what form it takes, is notoriously hard to assess. The politicians of Northcliffe's day undoubtedly believed, as their contemporary successors do, that great newspaper barons wield great influence, and acted accordingly. Both they, and Thompson, might have found it worthwhile to question this assumption more.

This book is scrupulous, well researched and strives constantly for balance. It has a "newspaper of record" quality, perhaps befitting a proprietor of The Times. But its most striking achievement is one that reflects the basic failing of newspapers of record, that it contrives to make a rumbustiously eventful life almost dull.

Huw Richards is the author of The Bloody Circus: The Daily Herald and the Left.