Report by Ronke Phillips
A murder investigation has been launched into the disappearance of a father who vanished more than five years ago.
Robert Duff was last seen on January 12, 2013, when he failed to arrive at a celebration for his daughter's 18th birthday. Despite a lengthy missing persons inquiry police now believe he was killed that night.
Searches are being carried out in open spaces near where he was last seen, including in Waterlow Park, Highgate, north London, with police divers scouring ponds, and at a flat in nearby Bredgar Road.
Mr Duff's mother Helen Duff said: "Robert's disappearance has always been forefront in our minds, and although we have always suspected that he may have come to some harm, there has always been the hope that he would return to us one day.
Watch the original ITV London appeal
"Since hearing that this is now a murder investigation, that hope has been taken away from us and as a family we are devastated.
"Our only wish now is that Robert is returned to us so we can grieve together."
The breakthrough in the case came after a television appeal on ITV London Tonight in January, which led a new witness to come forward. At the end of February the case was passed to Scotland Yard's murder squad.
Detective Chief Inspector Luke Marks said that Mr Duff was involved in a fight with two men on the night he died. Two people were arrested on suspicion of murder on Monday and released pending investigation.
Mr Marks said: "It has been over five years since Robert's family have seen or heard from him. Every day they have had to carry on without knowing what happened to him.
"I am making an appeal to the public once again, to come forward and help us complete the missing pieces of the puzzle.
"I urge anyone who saw or heard from Robert Duff on January 12 2013 to come forward and share what they know; it may seem like nothing to you, but it might be the information we need."
Detective Chief Inspector Luke Marks
Mr Duff had been to the flat in Bredgar Road on the night he died, and several people were there. His bank card and mobile phone remain missing.
Describing the 42-year-old as "a well-known and likeable character" in the local area, Mr Marks said there was no obvious motive for someone to cause him harm.
The fight on the night he died appears to have been "spontaneous", he said.
Mr Duff was friends with a woman called Lana Purcell who is also believed to have been murdered, but police are not linking the two cases.
Anyone with information can call police on 020 8358 0200.