The Professionals S01 E08 Everest Was Also Conquered

"ANARCHY, ACTS OF TERROR, CRIMES AGAINST THE PUBLIC. TO COMBAT IT WE'VE GOT SPECIAL MEN..."

A dying man's confession triggers the re-opening of a twenty-year-old case of police corruption, an investigation in which the main prosecution witness was murdered by the police officers who were supposedly trying to protect her. Somebody then decides to silence these officers, and sets about doing so.