PETER THURGOOD and Lindy Benstead were shot at point blank range in April 1986.
Dubbed the lovers' lane murders, the pair were known to be having an affair and were found dead together in a car but the killer has never been caught.
Who are Peter Thurgood's children?
Peter Thurgood, 46, is survived by two children who have continued to seek justice for their father who was killed in 1986 in West Sussex.
Terry Thurgood
Since his father's death, Terry Thurgood, along with other family members, has tried to get closure.
The 52-year-old lost his father, Peter, over 35 years ago when Peter was shot at point blank range in a car which he had rented.
Terry remained friends with the son of the other victim Lindy Benstead.
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David Thurgood
Peter's other son David has also tried to find justice for his father, he was only 15 years old when he lost his dad.
He said: "It's been 35 years. I was only 15 at the time. It's taken away my childhood and I felt it every day since."
The pair, along with Lindy's daughter Karen, have urged people to come forward.
Missing evidence and lack of new information means this double death mystery is unlikely to be solved without a confession.
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What have they said on Peter Thurgood's murder?
The brothers said they believe that "somebody must know something".
A senior detective admitted to the brothers that there were gaps in evidence so it is unlikely to be solved without new evidence or admission of guilt.
Terry said: “The investigation from the start has been bungled. I’d rather have Scooby-Doo investigating my dad’s murder."
Maureen, mother of David and Terry, died from Covid aged 86 in 2020 but Terry said she never got over Peter's death.
He said: "It was soul destroying for her. It has been for everyone."
A joint statement from both the Thurgood and Benstead family said: "These terrible killings of our loved ones have haunted both families for 35 years now, and we remain united in our desire to support any enquiries that will help bring justice and closure for us all.
"We ask anyone who has any information they have not yet brought to the police, to come forward now."
David and Terry asked for people to come forward in order to give the family closure.
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One lead took investigators to America but came up blank, Lindy's husband was also a suspect but had a clear alibi.
Anyone who has information can contact Sussex Police online or by calling 101, quoting Operation Bardwell.