The heartbreaking and horrific story of how an identical twin was stabbed to death by a complete stranger will be aired on national television.

Anne Cook, 35, was killed when she was walking her dog in Munden Park, near the A41, in 2000.

She was stabbed in the heart with a kitchen knife by complete stranger, Leon Paul Amos, from Watford, who was convicted in 2001 and sentenced to life in jail.

Now, channel Crime + Investigation will be looking back at one of the most tragic cases the area has ever seen in a documentary aired on October 15 at 9pm.

Miss Cook, an internet designer, who was survived by her twin sister Susan Cutler, was walking her King Charles Spaniel, Elvy, when she was attacked by bare-chested Amos.

Amos, who was 35 at the time, had stalked another woman earlier that day, had a previous conviction for rape and had also held a woman at knife-point with the intention of raping either her or her daughter.

The court heard that Miss Cook, who carried a small lock knife, was stabbed through the heart by Amos in Watford, on May 9, 2000. She had been given the knife by her brother-in-law because she had become increasingly terrified of being attacked.

Amos then took her knife and her mobile phone.

Although she bravely tried to fight him off, he plunged a knife into her heart and then fled the scene.

Amos, who denied murder, took Miss Cook's mobile phone before running through bushes, scaling a 6ft fence topped with razor wire and crossing six lanes of the M1, forcing cars to swerve to avoid him.

He was arrested nine days later.

After he was convicted, Susan said of her sister: “She was a hard working, honest and lovely person. She wasn't my best friend, she was my second self."