A man who fought for 20 years to find out how his son died after a party at Michael Barrymore's home has died, a friend said.
Terry Lubbock, 76, from Harlow, Essex, revealed earlier this year that he had been diagnosed with terminal cancer.
He had campaigned for justice for Stuart, 31, who was found in the TV presenter's pool in Roydon, near Harlow, in March 2001.
Friend Harry Cichy paid tribute to his "tenacity and determination".
"He thought about Stuart every waking hour, seven days a week," he said.
"He's died sad, knowing people never knew the truth about what happened."
The senior investigating officer from Essex Police vowed inquiries would continue and made a fresh appeal for information.
No-one has been charged with any offence in relation to death of Stuart Lubbock, who had been attending a party at Mr Barrymore's home with eight other people.
He was found unconscious in the entertainer's swimming pool, and alcohol, ecstasy and cocaine were detected in his bloodstream.
He died at Harlow's Princess Alexandra Hospital, police said.
A post-mortem examination found he had suffered "horrific" injuries prior to his death.
A coroner recorded an open verdict, but Terry Lubbock had asked for a fresh inquest.
Last month a man arrested on suspicion of murder and indecent assault was released without charge.
Det Ch Insp Jennings said: "Terry's devotion to his son and to his pursuit of justice knew no bounds. He was an example to many of us in his relentless quest for truth and justice.
"Our investigation into Stuart's death will not end with Terry's - as long as the case remains open, we will do all we can to deliver justice for him and his family.
"To this end we urge anyone who has information about Stuart's death to please now, more than ever, do the right thing and come forward."