Police hope a £20,000 reward will encourage someone who went to a sinister youth club frequented by paedophiles to unravel the mystery of what happened to a teen missing for 26 years.
North Cheam boy Lee Boxell was 15 when he went missing on a warm September afternoon in 1988.
To mark what would have been his 41st birthday on Sunday, police have offered the maximum £20,000 reward to anyone who can give them information that leads to them finding his body or the prosecution of those involved.
Police say the answer lies within a small number of people in the area who went to the Shed youth club in St Dunstan's Church, Cheam.
Detectives know the unofficial club was frequented by paedophiles who preyed on disaffected youngsters who went there to drink and smoke.
They fear Lee, who is known to have visited the Shed, could have fallen victim and want anyone else who was abused at the club - or even someone who carried out the abuse - to come forward if they can help find Lee and get some answers for his family.
Lee's dad Peter has backed the police's effort and described it as possibly his "last chance" to find out what happened to his son.
During a press conference on Monday, investigating officer Detective Inspector John McQuade said: "Kids as young as 12 and 13 went there regularly. They were vulnerable by age and circumstance.
"We know that there was paedophile activity there and we believe that quite a few of the people who went there were victims but we want them to come forward if they can help.
"There will be people who are concerned about implicating themselves but there is a big difference between knowing what happened and being responsible.
"Twenty-six years on, there will be people who have lived with this secret for a long time. Maybe, with the passage of time they can come forward."
Mr Boxell said he has not completely given up hope of his son coming home but said he now acknowledges it looks unlikely.
He said: "This is our last chance to find out what happened.
"I desperately need to know what happened, where his body is if he has been murdered.
"We need people who went to that club to come forward and say who they saw.
"Please come forward. I'm not getting any younger. I'm 67 now and I've waited over 25 years to find out what happened - please don't make me wait any longer."
VIDEO: Sutton Borough Commander Detective Chief Superintendent Guy Ferguson, Lee's dad Peter Boxell and Detective Inspector John McQuade at the press conference
Lee was last seen in Sutton High Street on September 10, 1988. It was initially thought he went to a football match at Selhurst Park but he never went to the ground.
Instead, he is thought to have visited the Shed and come to harm.
Lee was wearing a Swatch watch like this on the day he went missing. Police believe his killer may have kept it as a trophy.
The Metropolitan police carried out its largest forensic archaeological dig at the church but have not found Lee's body, although DI McQuade said they still think he is buried in the area.
Officers said the Shed was known to be visited by paedophiles for several years in the late 80s and early 90s.
St Dunstan's Church had did not know about the abuse. The building was replaced with a new community centre in 2010.
Anyone with information can call the incident room at Sutton police station on 0208 721 4005 or the charity Crimestoppers on 0800 555 111.
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