Tomalin triumphs over her husband to take top literary prize

A political turncoat, serial seducer and corrupt civil servant last night emerged as the hero of this year's Whitbread Book Awards. Claire Tomalin's biography of Samuel Pepys, the naval administrator whose frank diary illuminates 1660s London, won the £25,000 prize by an "overwhelming'' vote.

Ian Hislop, the Private Eye editor who chaired the Whitbread judges, praised the winner's ability "to go well beyond the source material'' in painting a panorama of a dramatic life in turbulent times. The judges admired Tomalin's book – the third biography of Pepys in a generation, but the first by a woman – for presenting "a wonderful introduction, not just to the diaries but to an astonishing piece of history''.

Reviewing the book in The Independent, Diana Souhami called it "a vivid chronicle of contemporary history seen through the all-too human preoccupations of this ordinary and extraordinary man''.

Tomalin, the bookies' 5-4 favourite, beat off a strong challenge from her husband, Michael Frayn. His novel Spies, already winner of Whitbread's fiction award, was commended by Ian Hislop as a "beautifully written'' account of a war-time childhood which the judges enjoyed hugely. Tomalin's success is the first overall victory for a biography in the Whitbread since 1991, and the first for a woman writer since novelist Kate Atkinson won in 1995.

Although the domestic rivalry between Frayn and Tomalin attracted most media attention this year, the judges also praised the other category winners. They included Paul Farley's collection of poetry The Ice Age; Hilary McKay's children's novel Saffy's Angel, and The Song of Names by journalist Norman Lebrecht, the victor in the first novel category.

Born, like her husband, in 1933, Claire Tomalin was literary editor for the New Statesman magazine and The Sunday Times. She published her first biography, of the pioneer feminist Mary Wollstonecraft, in 1974. Other acclaimed books include lives of Charles Dickens' mistress Ellen Ternan and of Jane Austen.

Her study of Pepys, subtitled The Unequalled Self, is her first portrait of a man. It moves beyond the reports of the Restoration in Pepys' diary to explore the ups and downs of his career as an architect of the Royal Navy. Tomalin also looks at his energetic extra-marital liaisons with a sympathetic but often ruthless eye. The Whitbread judges relished her description of how public servants abandoned Oliver Cromwell's Commonwealth to back the restored monarchy.

In an age when public life is as confused as ever about the boundaries of personal and political behaviour, Tomalin's account of a full life allows us to understand these contradictions. Pepys "looked at himself with as much curiosity as he looked at the exterior world'', says Tomalin. His self-knowledge is perhaps just as necessary for today's civil servants.