The brother of a schoolgirl murdered 50 years ago has told of the emotional toll the killing has had on his family as he appealed for anyone with information to come forward.
Elsie Frost, 14, was stabbed to death on a canal towpath in Wakefield in 1965 but no one was ever convicted for the fatal attack.
Colin Frost said his parents, Edith and Arthur, had died "with a huge amount of guilt" and he had gone "through a whole range of emotions" during his life.
Mr Frost said Elsie had been like a mother to him, adding: "She was just a sweet, sweet person. She was lovely."
Police, led by Detective Chief Inspector Elizabeth Belton, have launched a public appeal and are seeking information about a "butcher or abattoir worker" who was seen cycling near where she was found dead.
Officers also want to identify someone, "possibly a boyfriend", who may have been meeting Elsie in secret in the days before her death.
Mr Frost told BBC Radio 4's Today programme: "Throughout my life I have gone through a whole range of emotions, anger and more recently one of great emotion and I feel quite emotional even now.
"I would sincerely just ask anybody to come forward with any kind of information to DCI Belton and her team just to help.
"We need to get some justice for Elsie and we need to get justice for the people of Wakefield, who have never forgotten this."
Mr Frost said he and his sister Anne "remain confident" that the fresh investigation will turn up new information.
He added: "Both our parents died with a huge amount of guilt and when Anne and I decided we were going to press ahead with this we actually said we didn't want to die thinking we had not done anything."
Elsie was attacked on October 9 1965 as she walked home through a railway tunnel near the Calder and Hebble Canal towpath.
Her body was discovered at the foot of a set of railway service steps by a dog walker at around 4.15pm.
DCI Belton said: "Elsie's death may be many decades ago, but the pain of her loss remains as fresh as ever for her brother Colin and sister Anne.
"Her brutal murder shattered their family and with such a significant anniversary near, I would ask anyone who may not have come forward then, for whatever reason, to do so now and provide them with answers."
She added: "We now believe at least one person, who was never interviewed at the time, was seen near the location where Elsie was murdered on the canal towpath.
"He was described as white, 25 to 30 years old and riding a black bike with a basket on the front and wearing a white lab-type coat possibly of the style then worn by someone who could have been a delivery boy, butcher or abattoir worker.
"Inquiries also suggest that when staying at a friend's a couple of weeks before the murder Elsie got dressed up and went out, possibly to meet someone.
"Elsie's murder may be nearly 50 years old but it is a crime people in Wakefield have never stopped talking about."
The re-investigation of the case was prompted by a BBC Radio 4 investigation into the case.
Ian Bernard Spencer, then aged 33, was charged with the murder and cleared on the orders of the judge who heard the case at trial in 1966.
Anyone with information is asked to contact the major investigation review team on 101.