Clapton's son, Conor, was 4 years old in March 1991 when Clapton took him out on their first father-son outing together. He shared Conor with Italian actress Lory del Santo, his mistress who he impregnated while married to Pattie Boyd, whom was previously married to George Harrison.
During their outing, Clapton took Conor to the circus at Nassau Coliseum on Long Island.
"When they returned to the apartment, with Conor chattering excitedly about the clowns and elephants, Eric told Lory that, from now on, he intended to be a proper father," Norman wrote in the biography.
But tragedy struck the next day, when Clapton was set to pick up Conor for another visit, this time to the Bronx Zoo.
"In the morning, as mother and son waited for Clapton to pick Conor up from the apartment, a janitor arrived to clean the windows," the biography reads. "Lory was in the bathroom and the boy was in the care of a nanny – but careering around in a state of high excitement, impatient to see his ‘Papa’ again."
"The janitor had been working on the cantilevered windows in the living-room, one of which still hung open. He called out to the nanny to watch the child, but before she could react, Conor dashed past her, jumped up on to the low window-ledge where he’d normally press his nose against the glass to gaze out – and disappeared," it continues.
A frantic del Santa called Clapton to deliver the horrific news. "She managed to convey that he had fallen through an open window, but the idea was unimaginable to Eric and all he could find to say was: 'Are you sure?'"
"'Whatever physical damage Conor suffered in the fall, by the time I saw him they had restored his body to some normality,'" Clapton recalled in the biography. "'I remember looking at his beautiful face in repose and thinking, 'This isn’t my son. It looks a bit like him, but he’s gone.'"
Norman went on to write that the funeral was attended by George Harrison, Phil Collins and other big names from the music industry, and that "hundreds of letters and messages of condolence had poured in from all over the world, including one from Prince Charles."
Months later, he wrote his first song since his son's death, "Tears in Heaven," which Norman describes as Clapton's "grief-soaked tribute to Conor, which became one of the biggest hits fo the 1990s."
Slowhand: The Life and Music of Eric Clapton hits bookshelves on Tuesday, Oct. 30.