It has been 29 years since Ms Nickell was stabbed 49 times by Robert Napperin a frenzied attack in front of her little boy on Wimbledon Common.
At the time, the heartbreaking story was in a storm of headlines in the 1990s.
In a new interview, her son Alex Hanscombe remembered walking hand-in-hand with his mother in the moments leading up to her murder.
He told MailOnline: “I remember a stranger walking up towards us. I remember being grabbed and thrown around roughly.
“And I remember my mother being grabbed and thrown around, collapsing on the floor beside me. And I remember the realisation of what happened.
“I said: “Wake up, Mummy.’ And she didn’t respond. So I said again: “Wake up, Mummy,” and she didn’t respond. Even as a three-year-old child, I knew my mother was gone. She wasn’t coming back.”
His dad Andre moved his young son at the time to South of France and then later to Barcelona.
The move caused a rift with Mr Hanscombe’s grandparents at the time.
The father and son taken part in upcoming documentary Death On The Common: My Mother’s Murder which will air next week.
Recently, they have been watching Channel 4’s miniseries Deceit which tells retells the story of a honeytrap operation against innocent man Colin Stagg who was the first suspect in Ms Nickell’s murder.
Stagg received more than £700,000 in compensation for the controversial operation.