David Kelly was the British scientist and WMD expert (I met him once at an anthrax meeting in 1998) who leaked information to the BBC that Tony Blair's government had "sexed up" (read "made up") its report on Iraqi WMD. Soon he was found dead in the woods near his home.
The Telegraph explains that no inquest was ever held regarding Kelly's death. Several medical experts have remarked on the unconvincing evidence for suicide during the past few years.
The Daily Mail adds more detail to the story, discussing the incestuous Hutton Inquiry (which supported Kelly's death as a suicide) methods and findings.