By the end of the tumultuous decade that was the 1960s, Allen Klein was the most powerful man in pop music through his control of the business affairs of both the Beatles and the Rolling Stones. Yet his triumph was as short-lived as his methods were controversial, and his relationship with both groups soon ended in rancour and litigation.

Infamous for his brutal methods and less than scrupulous financial probity, his reputation for shady dealings was enhanced further when, in 1979, he was jailed on charges of tax evasion. Yet even after his disgrace, through his company ABKCO he continued to control many of the most influential recordings in popular music, including much of the Rolling Stones back catalogue.

Allen Klein was born in 1931 in Newark, New Jersey. His mother died of cancer when he was an infant and his father — a kosher butcher — put him and his three sisters in a Jewish orphanage. By the time he returned to the family home at the age of 12, he was worldly-wise beyond his years and living on his wits.

Leaving school early, he worked as a newspaper distributor and paid his own fees to study accountancy at night school. His first involvement in the music industry came in the early 1960s, when he volunteered his services to the Texas rockabilly singer, Buddy Knox. In a technique that was to become his trademark, he audited the books of Knox’s record company, claimed to have found irregularities in the royalties due to the singer and hit it with a lawsuit. It settled out of court.

When in 1962 the singer Bobby Darin received what was then a record $750,000 advance from Capitol Records, Klein struck again. At the party to celebrate his signing, Darin was surprised to be approached by a short, stocky figure who thrust a cheque for $100,000 into his hand. “What’s this for?,” the singer asked. “For nothing,” Klein replied.

Somehow he had managed to get a look at the books of Darin’s former record company and found a six-

figure discrepancy. His deal for not going public was that he be allowed to deliver the payment to Darin person-ally. The singer promptly sacked his accountants and gave Klein the business. “Most record companies were ripping off their artists so badly that all Klein had to do was nose around and threaten legal action,” observed the author Barry Miles, who years later researched Klein’s methods.

Buoyed by these early successes and a seemingly bottomless supply of self-belief, Klein’s calling card became: “You want a million dollars? You got it,” or, alternatively: “I can get you double”. His next client was Sam Cooke and he was as good as his boast, negotiating the singer a million-dollar deal with RCA in 1964. Unfortunately, Cooke was shot dead a few weeks later.

Despite this tragedy, new clients claiming that they had been robbed by unscrupulous record companies were soon queueing at the door of his Broadway office. But as the “British invasion” of the US charts gathered pace, Klein was looking overseas to make his next financial killing. Forging a partnership with Mickie Most, he helped the British producer to a million-dollar production deal with Columbia Records.

He also negotiated lucrative contracts for some of the acts produced by Most, including the Animals, Herman’s Hermits and Donovan.

Yet his sights were set on a grander prize and he told colleagues that his ultimate ambition was to manage the biggest group in the world, the Beatles. At the time they were still under the shrewd stewardship of Brian Epstein. So Klein first targeted their main rivals, the Rolling Stones, befriending the group’s manager, Andrew Loog Oldham, and offering to help renegotiate the group’s contract with Decca.

It would be an exaggeration to say that the Stones immediately fell for Klein’s charm. But they certainly liked the money he talked. Keith Richards later described their first meeting. “In walks this little fat American geezer, smoking a pipe, wearing the most diabolical clothes. But we liked him, he made us laugh and at least he was under 50. There was a new deal with Decca and Andrew told us Klein was a fantastic cat for dealing with those people, which we couldn’t do.”