The film sprang from a Vice article about a subculture of gay men that uses drugs to fuel unsafe sexual activity, often in weekend-long parties. Speaking to clinic counsellor David Stuart and several men from the scene, the filmmakers piece together a story of men who use semantics to deny the fact that they're junkies: they slam chems rather than inject drugs. But the fact remains that using chemicals like ketamine, mephedrone, crystal meths and especially GHB reduces the ability to make sensible decisions about health and safety.

Essentially, this is a depiction of the toxic cocktail of drug abuse, HIV infection and endemic social homophobia, which has left gay men feeling inadequate in pretty much every way imaginable. The film slightly overstates the issue, sounding like every gay man in London is shooting up and having dangerous sex. But perhaps a jolt of fear is needed to grab the attention. All of the men interviewed know that they need to escape this destructive cycle, wand their efforts offer real hope.

Shot and edited to a high standard, with an emotive electronic score by Daniel Harle, the film has a very strong impact as it delves deeply into this scene. Interviews are honest and sometimes painfully emotional, and the camera crew follows the guys into some rather astonishingly graphic situations involving both drugs and sex. Some of these scenes feel assembled for maximum scare value, adding a moralistic slant to the entire project. But there is also truth in every scene, and a willingness to present the issue as it really is rather than hedge around it.

The most potent aspect of this film is the way it portrays young men who have grown up knowing they weren't accepted for who they are. So it's predictable that some turn to drugs, which in turn removes barriers to forbidden sexual experimentation. This is also reflected in attitudes to HIV, as so many of these guys feel like they might as well just get infected so they don't have to live in fear of it any longer. In other words, chemsex is a symptom of something much bigger in society, so what needs to be addressed goes far beyond getting these men into rehab.

Arrested at 20 in 1982, Nick Yarris spent two decades on death row in Pennsylvania for a crime he claimed he didn't commit, battling through appeals and trying to have the evidence re-examined using newly developed DNA tests. He describes years of solitary confinement in an area of the prison where the guards demanded complete silence. An escape attempt is chaotic and suspenseful. And he even falls in love and marries his chief advocate. But with the court dragging its heels, Nick finally petitions the judge to stop dithering and carry out his death sentence.

Sington wisely lets Yarris' words narrate the events without adding any other interviews. He's a superb storyteller who recounts every anecdote with vivid literary detail and raw emotion, so the audience hangs on every word. Even brief sideroads carry a real punch, such as an incident in which two fellow inmates were painfully separated by a change in prison policy. Yarris uses music and books as key references in his life, so Sington brings both into the film, beautifully augmenting Yarris' words.

There are also artful re-enactments of the events, including the various crimes that resulted in Yarris' imprisonment. But these are shot with remarkable sensitivity, never showing faces while drawing out details in Nick's narration. Combined with dream-like imagery of himself as a younger man and boy, the audience is allowed right into Yarris' mind to experience his memories firsthand. This sets us up for a series of twists and turns later on that completely redefine everything that's gone before.

The film is elegantly shot and edited, with an emotive score by Philip Sheppard. Most of the screen-time centres on Yarris' expressive face as he tells his frankly astonishing story, and it's impossible to look away. With its surprising series of events, the film brings to mind recent documentaries like The Imposter and Searching for Sugarman, which also recound true stories in ways that are mesmerising and deeply affecting. And without ever shouting its themes, the film has a lot to say about a justice system that plays to prejudices and expectations rather than the truth.

The film opens as Brando explains that he has had his face 3D digitised, and this spectral image offers a variety of monologs along the way. The film also returns repeatedly to news clips from the notorious 1990 shooting at Brando's Los Angeles mansion. In between, Brando narrates his life story to himself in private cassette recordings. He discusses his troubled childhood, marriages and children, and shares anecdotes from several film sets. He also discusses bigger philosophical issues and his strongly held political views, which led to activism on civil rights and native American issues.

The most interesting topic Brando discusses is film history, exploring the changing nature of movies through his career and how acting itself has shifted. He trained in Stanislavski's Method with Stella Adler, and notes that this raw new style changed cinema permanently, ushering in much more realistic performances. Indeed, Brando was continually criticised for his too-honest acting, and the press often confused his believable roles with who he was in real life.

But he opens up about his mercurial personality, including loud disagreements with everyone he worked with. He loved the rush he got from acting, women and travelling the world, including his beloved adopted home in Tahiti. All of this is accompanied by a blinding array of stills and clips that show the articulate Brando charming (and flirting shamelessly with) journalists. And he also examines acclaimed classics like A Streetcar Named Desire and The Godfather; bombs like Candy and A Countess From Hong Kong; and challenging productions like Last Tango in Paris and Apocalypse Now.

The course of Brando's life has been public record, but this is the first chance to see it through his eyes. The most notable nuance is Brando's easy humour, refusing to take himself seriously even as he throws himself into a series of heated causes. Brando made these recordings for himself, as a sort of therapy. So even if filmmaker Riley has extensively edited the material (which is audible as the quality and tone shifts), there's a sense that Brando's real thoughts are finally being heard.

From the screen tests of the original Not Ready for Prime Time Players, the film traces four decades of Saturday Night Live, which wasn't expected to last six weeks. But it hit a nerve right from the start, becoming the first truly unmissable TV show. After five years, the exhausted cast left. So over the years the show has refreshed its ranks, moving through several highs and lows. Today it's a global franchise. It still has the same format, but is less homespun and raw, more institutionalised and sponsored. And the biggest change is that now you don't have to watch it live. Today the good sketches go viral on YouTube, and anyone can make their own Wayne's World.

Director Nguyen includes interviews with cast members, hosts and public figures, plus lots of hilarious clips. SNL was aimed at the first generation to grow up with television. So it could tackle gender and racial barriers in unusual ways, even though it was controversially sexist at times and always had a diversity problem. It has also steadily celebrated female comics and gave the world Eddie Murphy.

The documentary emphasises the show's political sketches. It was born just after Vietnam and Watergate, when people wanted to hear from voices who weren't in the establishment. Weekend Update countered the establishment way of reporting the news long before The Daily Show. Throughout SNL's tenure, the goal has been to comment on society in ways that are smart and funny while avoiding partisan politics. And the show has changed the way people see public figures. Yes, Chase's Gerald Ford is more memorable than the actual man.

While it concentrates on the classic sketches, the film is also critical, diving into on-air controversies, clashes with censorship and pressure from social critics and network executives. It's a striking depiction of the challenges and chaos of live TV and the extended family that puts Saturday Night Live together. The show's strength has always been its ability to joke about issues people are afraid to laugh at, so it has had a strong impact on both television and society. Four decades later, it's still relevant. Which is why it's still here.