HUMPHREY CARPENTER’S early death deprives the world of a prolific biographer, BBC radio of a uniquely knowledgeable and lively broadcaster, and the city of Oxford of a loyal son. He was an eccentric, unpredictable entertainer and a man of intense kindness who combined a powerful instinct for mischief with an absolute lack of malice, and very little vanity.

Humphrey William Bouverie Carpenter was born in 1946. His father, the Right Rev Harry Carpenter, became warden of Keble and later Bishop of Oxford. Humphrey, an only child, was brought up among books and was expected, he said, to think for himself as soon as he could walk; his mother, Urith Monica Trevelyan, was a Froebel-trained teacher. He went to the Dragon School, itself famously offbeat at the time, then to Marlborough and Keble College, Oxford. He joined the BBC as a general trainee but was drawn back to his home town for the launch of BBC Radio Oxford in 1970.

Here he demonstrated the dual talents for scholarship and merriment which marked his later literary career. He sewed together “town” and “gown” interests, always mutually suspicious, by persuading eminent dons to broadcast in a lively popular idiom, particularly on local history. At the same time he appeared on Saturday mornings as “Humf”, a fast-pattering and technically intricate disc jockey whose parallel life was studded with imaginary characters and Goonish voices.

Few distinguished literary biographers enjoyed such a louche professional start, but his instinct to entertain and mildly outrage more staid personalities is discernible through much of his career. While at Radio Oxford he married Mari Prichard, daughter of the Welsh poet Caradog Prichard. Her calm, tidy nature diametrically opposed his own.

Music mattered intensely to him: he was a skilful pianist, but more lovingly played the double-bass, bass saxophone and sousaphone, which comically awkward instruments frequently made it difficult to negotiate a path through the family sitting room. His battered cars were as familiar a sight as the lean, beaky profile with its mop of unkempt collar-length black hair travelled erratically around North Oxford with gigantic instruments astern. His ensemble, Vile Bodies, played 1920s and 1930s dance music and jazz, and held a residency at the Ritz Hotel in London for seven years from 1987.

He had, by that time, escaped his BBC job and been freelance for more than a decade. His first book, A Thames Companion (1975), written with Mari Prichard, was a guide to the river, which the pair had navigated from sea to source in a small boat, camping out.

In 1977 he wrote a biography of J. R. R. Tolkien, and in 1978 one of his most characteristic and important books, The Inklings. This showed his early mastery of the difficult form of group biography, tracing the literary, religious and personal relationships of Tolkien, C. S. Lewis and Charles Williams and their meetings in an Oxford pub. It trod a delicate, and typically Carpenter, line between amusement at the men’s eccentricities, respect for their work, and human sympathy. It won the Somerset Maugham Award. Further awards were earned by his next biographies: of W. H. Auden, Ezra Pound, and Benjamin Britten — in each case he combined passion for their work with gossipy relish for absurdity and great empathy. Like many of his subjects, he suffered bouts of serious depression.

Some attacked him for his breezy openness about the sexual oddities of his subjects, notably Britten and Dennis Potter, but his research was rigorous, his sources solid, and if there was a difference between him and his critics it was that he was slower to condemn the strange byways down which life leads nervous and creative people.

His feeling for group biography led to his interspersing his serious biographies with shorter, lively sketches including Geniuses Together, a study of American writers in Paris, a chronicle of The Angry Young Men of the 1950s, The Brideshead Generation about Evelyn Waugh and his friends, and That Was Satire That Was, about the satirists of the 1960s.

Carpenter’s amiable inquisitiveness tended to bring him scoops. Indeed, his publishers and agents often trembled at his barely curbed instinct to retail these to his many friends, with whoops of laughter, in advance of publication. His 1996 biography of the former Archbishop Robert Runcie caused the greatest furore, because Runcie dropped some revealing (though fairly harmless) remarks about his advice to the Prince and Princess of Wales before their marriage. Carpenter was accused of betrayal, and suffered violent and pompous attacks, notably from the critic A. N. Wilson, who decried him not only for treachery but also for his scruffily carefree personal appearance.

Carpenter bore no malice, and appeared, in public, unperturbed. There had been no off-the-record stipulations, and the Archbishop was suspected to be rather less annoyed than he was forced by decorum to appear. His note to the biographer saying he wished he had died before publication was read by the humourless as a terrible condemnation. To other eyes, it seemed that Lord Runcie shared some of his biographer’s old-fashioned Oxonian taste for mischief.

Carpenter felt he had done nothing unethical and remarked to a friend that it had been a dreadful trial of his integrity for months, having the royal marriage collapse in public while he held this material in his notebooks: “My car kept trying to drive in the direction of Wapping and a whopping cheque, and I had to rein it back.”

He had a lifelong feeling for childhood and its imagination: with Prichard he produced The Oxford Companion to Children’s Literature (1984), and his study of 19th-century children’s books, Secret Gardens (1985), is a modern classic. His own series of Mr Majeika books became a popular children’s TV series with Stanley Baxter, and led to a quixotic and unforgettable exercise in 1992.

Having two musical and dramatically adept daughters, he had founded the Mushy Pea children’s theatre company in Oxford. Having written them a lively jazz musical called Babes about the Judy Garland generation of Hollywood child performers, in whose style he coached the children to uncanny perfection, he spent his Majeika royalties on taking the entire cast of more than 50 to London for a run at the Shaw Theatre. “If you have an idea that sounds fun,” he remarked, balancing in a coachful of excited children as it thundered across London to a cast party during this hectic enterprise, “and you can just about afford it, you really have to do it, don’t you? Never know how long you’ve got.”

As time went on he was ever more noted, by children and by younger writers, for his glee in discovering talent in others and his generosity in providing ideas for their creative output. In his early fifties he was struck by Parkinson’s disease, which progressively disabled him, though he insisted that his friends conceal this fact from the BBC in case it hesitated to use him on the arts progamme Night Waves — which he pioneered — and In Tune.

Nor did his courageous spirit and industry flag. His history of the publishing house John Murray, in the last stages of revision when he died, gave him particular gossipy joy. He is survived by his wife and two daughters.

Humphrey Carpenter, writer and broadcaster, was born on April 29, 1946. He died of a pulmonary embolism on January 4, 2005, aged 58.