One of the powerful aspects of Fergie's closeness to the terror attacks was the famous rag doll uncovered by photographers from the rubble in the aftermath.
The Duchess had been provided with an office on the 101st floor of the North Tower for her charity Chances for Children.
Initially mistaken for a child's doll, it was later revealed that Fergie had created the ragdoll as a mascot for her fundraiser (naming it Little Red).
"When it came on TV, I looked and saw Little Red and the presenter said 'Oh look there's a child's doll!' and I immediately called up the presenter and said please, don't worry," the Duchess told the BBC in 2014.
"Because I was so worried they would think that a child was lost or buried in the rubble.
"So I said no, it's not a child's doll it's Little Red and she is a symbol for Chances for Children."
Fergie went on to write a series of books based on the character of Little Red and the original mascot became part of the 9/11 memorial exhibit on Ground Zero.
Speaking at an event in 2006 for the fifth anniversary of the terror attacks, the Duchess’ ex-husband, Prince Andrew, also revealed how terrified he was for Fergie at the time.
The Duke had been on a plane to the United States at the time and was aware that Sarah was expected at her Chances for Children charity's office on the 101st floor of the World Trade Centre.
"It was difficult to remain calm when I had to sit in the plane unable to communicate with New York, knowing Sarah had an office in the World Trade Centre and was in New York at the time.
"I had some small insight into the anguish many families were suffering that day."
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