One account had Frank Sinatra putting the Mob on to him, believing that his daughter Nancy and Hazlewood had grown too close.But the more prosaic reality was that Hazlewood had simply decided to begin a new phase in his career, of which the Sinatra years formed a small part.Lee Hazlewood, who died on Saturday aged 78, was one of the most influential figures in 20th-century pop; most famous as Svengali to Nancy Sinatra, for whom he wrote These Boots Are Made for Walkin', he was also an important influence on Phil Spector's "Wall of Sound" recording techniques, and his songs have been covered by stars from Elvis Presley and Dusty Springfield to Nick Cave and Courtney Love.

But when Reprise suggested she move on to duets, she insisted that only Hazlewood would do.

They went on to record several hits together, fusions of country, pop and psychedelia, including the darkly ambiguous Some Velvet Morning, and Sugar Town.

Between 19 Hazlewood wrote and produced the better part of nine albums for Nancy Sinatra, including a number of hit singles.

At the same time, Hazlewood's droopy moustache and licentious, smoky southern drawl, evocative of a lifetime's hell-raising, earned him a cult following.

Hazlewood was reluctant, but after Sinatra himself lured him to the family home for a drink and thanked him for agreeing to help, he felt it would be unwise to demur.

Hazlewood set about reinventing Nancy as a "tough little broad", dyeing her brown hair blonde, swapping her ballgowns for Carnaby Street fashions and persuading her to wear boot-polish black eye make-up and frosted lipstick. Hazlewood told her to sing it "like a 14-year-old girl who screws truck drivers" ("14" was later sanitised to "16" and "screws" to "dates"), and it sold five million copies to an audience blissfully unaware that, as Hazlewood put it, "anyone in my part of Texas knows that messin' [as in "You've been messin' where you shouldn't have been a messin"] means f*****'."Initially, Nancy Sinatra sang alone.The songs' scurrilous lyrics, with their thinly-veiled references to drugs and sex ("Some velvet morning when I'm straight/ I'm going to open up your gate") were part of the attraction.So too was the implication that theirs was more than a singing partnership, though Hazlewood maintained that they were just good friends and, in any case, Nancy, as a nice Catholic girl, never understood what she was singing about, having sensibly decided not to ask.The son of an itinerant oil driller and a half-Native American woman, Barton Lee Hazlewood was born at the small town of Mannford, Oklahoma, on July 9 1929, three months before the Wall Street crash.Then, at the height of his success, Hazlewood packed up and disappeared to Sweden.For the next two decades he remained elusive, refusing to sanction the re-release of his records and shunning celebrity.