The son of a Colchester schoolgirl who was murdered has described the horrific moment he watched his mother die.

Rachel Nickell was stabbed 49 times and sexually assaulted in front of her son Alex Hanscombe, then aged two, while walking their dog on Wimbledon Common.

The former Colchester County High School for Girls student was just 23 at the time.

The 1992 attack shocked the country and was one of the UK’s most high-profile cold cases until paranoid schizophrenic Robert Napper, 42, eventually admitted manslaughter.

Before his conviction, Napper also went on to brutally murder Samantha Bisset and her four-year-old daughter Jazmine the year after killing Rachel.

A new documentary called Death On The Common: My Mother’s Murder airs on Channel 4 tonight.

Gazette: Tragic - Colchester school student Rachel Nickell, who was brutally murdered and raped aged 23 in front of her young son

Alex has described the harrowing moment he knew his mother was gone.

Speaking on Lorraine he said: "Everything happened so quickly. I remember a stranger coming towards us out of the blue, being grabbed, dragged, roughed around, my mother being roughed around as well.

“Seconds later, my mother collapsed next to me. I picked myself up as fast as I could and yeah, was there a knife? Was there blood? All the details that people have talked about over and over again, absolutely but it doesn’t happen like in the movies, real life.

“It may be hard to believe, but to me she looked like she was lying there peacefully.

“I stepped towards her and I said: “Get up Mummy” and she didn’t respond. I said “Get up Mummy” once again and she didn’t respond. And I said it for the third time, “Get up Mummy” and in a split second - no matter how young I was - I knew that my mother was gone and that she was never coming back.”

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Alex appeared on Lorraine with his father Andre ahead of the documentary airing.

Gazette: Alex appeared on Lorraine with his father Andre ahead of the documentary airing

He added: “Somehow I felt there was a guiding hand on my shoulder, and I made my way out of the trees back into the open spaces where families were having picnics and they immediately came running towards me.

“They must have noticed the blood on my clothes and my battered face. In my memories, the ambulance arrived and I was put to sleep by doctors and woke up in hospital hours later so I still remember all that.

“You know what stays with me the most, you know that feeling that we’ve all had in our lives of being so close to someone and loving them so much and if you’ve ever gone through that to lose that, you know that feeling.”

The documentary comes after Deceit, a Channel 4 drama produced by Story Films and written by Emilia di Girolamo, explored the controversial honeytrap set up to catch a suspect in the case.