A man arrested on suspicion of the indecent assault and murder of Stuart Lubbock at the home of entertainer Michael Barrymore in 2001 has been released without charge.
The 50-year-old was arrested in Cheshire on 17 March after "significant new information came to light" following a TV documentary about the incident.
Essex Police said there was insufficient evidence for a "realistic chance of a successful prosecution" so the man had been released without further action.
Senior investigating officer, Detective Chief Inspector Stephen Jennings, said: "We have worked tirelessly to secure justice for Stuart, for his devoted father Terry and for the whole family.
"This news is a huge personal disappointment to all of the detectives involved in this case.
"We have explored all possible lines of inquiry and sometimes, regrettably, the evidence is not yet there to issue charges."
According to PA media, Stuart Lubbock's father Terry, who is seriously ill, wants police to review the decision.
Stuart Lubbock, 31, died at the home of Michael Barrymore more than two decades ago.
He had been attending a party at the entertainer's home in Roydon, in Essex, with eight other people on 31 March 2001.
A post-mortem examination showed Mr Lubbock had suffered severe internal injuries which suggested he had been sexually assaulted.
Alcohol, ecstasy and cocaine were found in his bloodstream.
The 69-year-old former television presenter, who is most famous for game shows and light entertainment programmes on British television in the 1980s, 1990s and 2000s, has always denied involvement in the death.
Barrymore was criticised for failing to answer questions at the inquest in 2002.
He told the hearing he could not attempt to save Mr Lubbock because he could not swim.
The coroner recorded an open conclusion.
Barrymore, former partner Jonathan Kenny and party guest Justin Merritt were arrested in 2007 on suspicion of sexual assault and murder.
They were later released without charge, with the star repeatedly denying any wrongdoing.