Marlborough: England's Fragile Genius, By Richard Holmes

Until a generation or so ago John Churchill, 1st Duke of Marlborough, vied with Wellington for the accolade of being England's greatest general. Now, thanks to History's optional place in the school curriculum, and teachers' concentration on Hitler and Stalin, he is an almost forgotten figure from an almost untaught period.

We should therefore welcome a new bio-graphy of the man who was so admired by Napoleon and (with unashamed ancestor worship) Winston Churchill – especially if the biographer is Richard Holmes, whose background is a happy blend of military academia and media friendliness. Professor Holmes tackles his subject at a Light Infantry pace, cracking through a wide-ranging biography with confidence and humour.

The first tenth of the book sets the context of Marlborough's life, thereby helping to explain the rise and fall of the handsome hero. Fashion, politics, and the brutality (and often brevity) of 17th-century life are all presented in a colourful slideshow.

Marlborough was born in 1650, at a time when traitors were hanged, drawn and quartered. Medieval methods still flourished after the English Civil War. This is not simply ghoulish embellishment to the duke's life story. It is relevant since, Holmes contends: "Marlborough lived on the margins of treason." Indeed, it is to the duke's moral code, rather than to any innate softness, that the book's subtitle, "England's Fragile Genius", is primarily addressed; that, and his vulnerability as a self-made man, reliant on that most fickle of commodities, royal favour.

John Churchill came to maturity in the reign of Charles II, the son of an impoverished Royalist cavalry captain who sent his children to Court to make good. Churchill's sister Arabella became one of the chief loves of the future James II. Churchill joined the Court as James's page boy, where he was extremely popular with his master: recognising the youth's fascination with the military, James gave John a commission.

Churchill's exceptional charm eased his upward path. His good looks were also deployed wisely. They resulted in an affair with Barbara Castlemaine, Charles II's most promiscuous mate (but not necessarily, as Holmes contends, "the most powerful of [the King's] mistresses" – that distinction surely goes to the French-born Duchess of Portsmouth?). For services rendered, Castlemaine gave Churchill £5,000. With typical thrift, he invested his bonanza; it formed the launching pad for his ambition.

It is to the roots of his power that Marlborough's fiercest critics have pointed. Thomas Babington Macaulay frothed with indignation at a career that he saw as being founded on the easy virtue of Marlborough's sister, and the generosity of his paramour. Holmes lets Macaulay have his say, before explaining that, in the moral climate of the Restoration Court, it is unfair to blame a young, penniless and ambitious young man for failing to eschew personal advancement and carnal pleasure.

Sarah Jenyns remains one of the grandes dames of British history. She shared John's impoverished, Royalist, background: Sarah and her beautiful sister were sent to find rich and titled husbands at court. However, she fell deeply in love with John Churchill, and they married. Their rise from the ranks of "distressed gentlefolk" to the pinnacles of political and military power was the supreme example of what Holmes refers to as a generation of people "rising without a trace". At one point John was just another fornicator in the Merry Monarch's Court. Thanks to his favour with the Duke of York, and his wife's passionate friendship with Princess Anne, they were the most powerful commoners in England.

Churchill's helter-skelter career saw him help save James II from the Duke of Monmouth's rebellion. However, three years later, alienated by his patron's increasingly strident Catholicism, Churchill deserted, and became a disaffected figure during the reign of William III, who gave him the earldom of Marlborough but effectively sidelined him. Yes, Holmes concedes, Marlborough was secretly communicating with the Jacobites; but this was merely insurance against a second Stuart Restoration.

Marlborough's chance for greatness came when Anne became queen, and straightaway joined the Grand Alliance against Louis XIV's France. For ten years Marlborough was victorious against a military machine that had not been defeated for over 60 years. Holmes is at his surest when writing about the great battles of the War of the Spanish Succession – he has a remarkable knowledge of the roots of the British Army, and an appreciation for Marlborough's legacy, which raised the English soldiers' stock from being vilified to becoming the troops most feared by the Sun King.

Holmes is less certain on general psychology. About Sarah and Anne's friendship, he writes: "It is never easy for men to grasp the depth and intensity of the love that can exist between women... partly because of men's fear that women's affection is in some way finite, and that the emotion which binds them to other women must necessarily limit that available for commitment to men." I found this an entirely unconvincing generalisation. There is no place for Marje Proops in this very good read, about a very great man.