Doyle, who graduated from Edinburgh University as a doctor, was the emotional antithesis of Holmes and anything but glacial with women.

Yet the Scot was to become obsessed with spiritualism and was ridiculed at the end as anEnglish eccentric.

This metamorphosis seemed odd to Lycett but "fitting since, from his start inEdinburgh, that city of contrasts, Arthur's life had been about crossing boundaries and trying to reconcile opposites".

These contradictions began in Picardy Place, where Doyle's English father Charles, an artist, brought his Irish wife Mary, and where Arthur was born in 1859.

Baptised Arthur for chivalrous adventures, Ignatius for the Catholic faith into which he was born and Conan for a cousin, each name was significant in the way the writer would shape his career. His parents' marriage was dominated by Charles's alcoholism, which would lead to his incarceration in an asylum. It was Mary who stoked Arthur's imagination with tales of knights and who realised he had a gift for telling macabre tales. It was to her that the graduate Doyle renounced his faith in favour of agnosticism. Even with the absence of a strong father, Doyle's close relationship with "Mam" was embarrassing. He sought her advice throughout his life, and in middle age wrote to her, "Was there ever such a love story as ours since the world began?"

If there was, it did not apply to his marriage. Louise, his wife since 1885 when he was practising as a doctor in Portsmouth, contracted tuberculosis in 1893. Doyle began secretly meeting a singer called Jean Leckie, 14 years his junior, for nine conscience-free years, marrying her soon after Louise died in 1906. At least she had encouraged Doyle to write something saleable to support their two children and, by filtering his medical knowledge through the new popular medium of crime stories, Sherlock Holmes was born.

Lycett excels in unearthing the sources from which Doyle drew to endow Holmes with unique skills, bolstered by his reading of second-hand books from James Thin's. Poe and Professor Bell of Edinburgh University led to Holmes, the rationalist detective, with shades of Stevenson and De Quincey.

Doyle's own transformation from rationalist to spiritualist is less easily quantified, but the first world war and the death from influenza of his wounded son, Kingsley, in 1918 all contributed. It was more than grief that caused Doyle to spend the rest of his life trying to use science to prove there was a spirit world.

Doyle's relationship with the children of his first marriage was distant. Hisson Kingsley had been uncommunicative when alive, but Doyle rejoiced when his chatty spirit contacted him through a medium shortly after the funeral. Guilt for neglecting the children and for renouncing his Catholicism intensified Doyle's spiritual fervour, and overshadowed his real achievements.

Doyle's fiction will always be dominated by the most celebrated detective in the world, a character he grew to despise and prematurely kill off, and who remains more famous than Doyle himself. His other writing will be read because of Holmes and better understood as a result of Lycett's brilliant analysis.