Police investigating a "significant breakthrough" in the shooting of a doorman in 1995 claim the "net is closing in on those responsible".
Ian Grant, 24, was found dead on wasteland in Cherry Hinton, Cambridgeshire, on 15 November 1995. He had been shot in the back of the head.
A new inquiry has been launched after new forensic evidence came to light.
Det Ch Insp John Hutchinson said: "We have been given a huge boost by the brilliant response so far."
He added: "We have had a number of calls including some from those who you might not expect to engage with police due to previous involvement in criminality.
"I'm optimistic that the net is closing in on those responsible for this shooting, but we still need people to come forward.
" I've no doubt that there are people out there who know what happened and have since moved on with their lives and are now settled with families.
"This is the perfect chance for them talk to police to draw a line under this terrible incident and distance themselves from having had any involvement.
"We've been really encouraged by the response from the community and it has made us even more determined to solve this senseless killing and bring Ian's family some closure after all this time."
Mr Grant was discovered near Fulbourn Hospital, close to his Cherry Hinton home, shortly after midnight
It is thought he had been killed between 20:00 and 22:00 GMT on 14 November.
His girlfriend's car had also been set alight outside their flat in Speedwell Close two weeks earlier.
Detectives still believe that incident is linked to the killing.
Mr Hutchinson said Mr Grant had developed "a lot of enemies" through his own violence and trouble with other door companies.
Two men were charged with conspiracy to murder at the time and acquitted after a trial at Norwich Crown Court.