Jon Smith, who pioneered the role of "super agent" in the world of football, said the player who almost single-handedly drove Argentina to the 1986 World Cup title was a Jekyll-and-Hyde character.
On the one hand there was a "lovely boy" from Buenos Aires and on the other there was the party animal whose life spiralled out of control.
Smith secured Maradona as a client after the 1986 World Cup finals by luck after two cancelled meetings, when he happened to be at Ossie Ardiles' house.
Ardiles, a 1978 World Cup winner with Argentina who had joined English club Tottenham, was on the phone to Maradona, who was looking for an agent, and the rest is history.
Smith said he was able to wield some influence over Maradona but it was limited as he was London and his client was in Naples, where he played his club football at the time.
Maradona's penchant for late-night parties, cocaine and women was almost as famous as his magical displays for Napoli.
"He had interesting people around him, shall we say," Smith said. "We supplied him with financial deals like Coca-Cola but there were a lot of other influences."
Smith said the Argentine, who died at the age of 60 on Wednesday, fitted the archetype of the "flawed genius".
"People talk about him being a flawed genius. Well I have met several geniuses and they all have flaws," he said.
"They have immense talent in their world but when you have done everything then what?
"Elvis (Presley) gets into drugs, Diego got to that point where his physicality had reached its peak and was going south.
"There were too many temptations, but for all the dark corners he shone a really bright light."
Clash of characters
Smith said the Argentine was a fascinating mixture of characters.
"He was two people really," said Smith. "There was Diego the lovely young man from the slums of Buenos Aires and he never lost that.
"He was a lovely boy and too nice in a way -- he could never say 'no'."
"Then there was Maradona who was the antithesis of that. He was the performer, the showman, the party man. He was everything little Diego was not.
"He was a complex character."
Smith, who initially forged a successful career in the music business, signed Maradona after he become the villain in the eyes of English football fans for his "Hand of God" goal in the 1986 World Cup quarter-final.
"The 'Hand of God', I did not spend a lot of time articulating about as it was not in my interest to do so," he said.
England goalkeeper Peter Shilton remains upset that Maradona never apologised for cheating by using his hand to score. But Smith said others were more than willing to meet the Argentine.
"When he was in London one time we had dinner with Gary Lineker and a few other people and they got on well," said Smith.
Maradona "was very charming but obviously there was a bit of hurt and angst," he added.
"It was hard, it was tough but it happened and life was moving on."
Smith said life was never boring with his illustrious client in five years as his agent, until his contract was suddenly terminated: "In 1991 the powers that be in Naples thanked me for a fantastic job but my services were no longer required."
One story sums up the mania that surrounded Maradona.
"When he was in Naples he liked collecting Ferraris," recalled Smith.
"One time I was there pre-lunch he took me downstairs to the garage to show me his latest.
"He had several and I noticed a few were badly beaten up. One looked like someone had walked all over it.
"In his worst English he said 'the problem is when I stop at red lights fans clamber all over them'.
"I think perhaps the best deal I ever did was convincing the Naples police to give him special dispensation to drive through red lights."