It's 40 years next month since Bobby Kennedy was murdered at the Ambassador Hotel in Los Angeles by a young Palestinian-American gunman, Sirhan Sirhan – or was he? O'Sullivan's film, which started life as a report for Newsnight, sets out to show that things weren't that simple.
Well, they wouldn't be, would they? The resulting film gives an impression of exhaustiveness, by virtue of some amazing footage of the night in question, not to mention sheer length; but you might start to wonder at the absence of anybody with a good word to say for the official version of events – I mean, somebody must have believed it.
In fact, like most conspiracy theorising, O'Sullivan's film relies on the assumption that every apparent inconsistency points to a deliberate untruth; but the version he leans towards, involving Manchurian Candidate-style brainwashing and the conjecture that watch-company executives may have led double-lives as CIA agents, strains credulity beyond repair.