Former milkman Colin Ash-Smith has been found guilty of murdering schoolgirl Claire Tiltman in a “frenzied attack” in 1993.
The 46-year-old stabbed Claire Tiltman from behind as she took a short cut through an alleyway to a friend’s house in 1993, four days after her 16th birthday.
Claire’s friends broke down in tears as the verdict was read out at Inner London Crown Court.
Ash-Smith stared straight ahead as the jury of seven men and five women gave their verdict after around three hours of deliberation.
After killing Ms Tiltman, he launched a second attack on another young woman, Charlotte Barnard, in the same town, Greenhithe in Kent, in 1995, leaving her for dead.
She was stabbed 14 times but survived and Ash-Smith was later jailed.
A search of his distinctive white Ford Capri uncovered one half of a school tie which police established had been used in the rape, kidnap and attempted murder of a 27-year-old woman in Swanscombe on 21 December 1988.
At the time of his arrest, Ash-Smith denied any involvement in Claire’s death when questioned by detectives.
But officers continued to examine the similarities between his other attacks and Claire’s death. A number of clues led back to Ash-Smith, including a prison confession and the fact that he attended Claire’s funeral.
Prosecutor Brian Altman told the court Ash-Smith had derived a “warped pleasure” from killing Claire.
He said: “Make no mistake, this was a killing for the sake of killing, carried out by a ruthless and predatory armed killer, who attacked his chosen victim rapidly and stealthily, allowing her no time for defence or escape, and who fled the scene just as efficiently as he had arrived.”
Cold case Detective Rob Vinson said the murder was one of the most “horrific” and “emotive” cases he had worked on.
“On the night in question Claire was in the wrong place at the wrong time.
“When you look at the writings and some of the things he has done, this is a very, very dangerous individual, and justice has been served at last for the brutal murder of Claire.”
Claire’s parents have died in the two decades since her killing and police say their deaths made officers more determined to catch her killer.
In a statement Claire’s family said: “A big thank you to the Kent Police who never gave up trying to find Claire’s killer.
“We would also like to thank Claire’s friends.
“Claire’s parents went to their graves convinced that Ash-Smith was Claire’s killer and with today’s verdict may they finally rest in peace.”