The Departed has stood the test of time. Released a decade ago, The Departed was an adaptation of Hong Kong thriller Infernal Affairs, but in Martin Scorsese’s hands the story became something much greater. Scorsese moved the setting to Boston, embedding it in the unique social and political culture of that city. In particular, The Departed is the most important film made so far about Whitey Bulger and the symbiotic relationship between organised crime and law enforcement which his career exposed.

The Departed was massive for the career of Leonardo DiCaprio, the role marking a major step forward from teen heartthrob to his status as arguably the world’s most important actor. His performance as undercover police agent Billy Costigan remains hugely compelling, with Costigan tormented by the guilt of the crimes he is complicit in, and in constant mortal terror of his psychopathic boss, the Bulger-esque Frank Costello (Jack Nicholson). One of the fascinating things the film gets right is that the thoughtful, educated, reflective Costigan is not cut out for the police force; as Dignam, says, he’s smart enough to be an astronaut, but he’s not a cop. Meanwhile, Matt Damon’s Colin Sullivan, who has been planted in the state police by Costello, is perfect cop material. Brash, selfish, and apparently uncaring, Sullivan has the perfect mentality for a police officer and the film charts his meteoric rise through the ranks.

The cast is stellar, and when you have a script as taut and exciting as this, it’s very easy to make everyone look good. Mark Wahlberg received rave reviews and an Oscar nomination for his entertaining performance in the relatively minor role of Sgt Dignam, while Nicholson, in probably his last great role, is extraordinary as Frank Costello. Costello is more than your typical charismatic psycho, his dialogue full of the kind of simple wisdom and criminal insight that helps lend the film a fundamental air of believability. Just as the story of Bulger’s career gives the film the necessary gravitas, so Nicholson’s own persona helps counteract the earnestness of Di Caprio’s performance, so that neither dominates the film completely.

The Departed is a film about Boston and a film about Irish America. A framing historical montage at the beginning of the film, narrated by Costello, covers the background of Boston’s race riots and Costello also explains his antagonism with the Sicilian Mafia in New Jersey. Most of the main characters identify as Irish and the film sympathetically portrays familiar Irish neuroses and personality types without straying into stereotype or pastiche. It’s characteristic of the film’s subtlety and depth that it is able to show characters with strong Irish pride as well as self-awareness of how their typically Irish failings affect or even control their behaviour. Curiously, it’s Damon’s emotionally stunted Colin Sullivan who offers the most explicit insights into Irish psychology. The film is also renowned for an inspired choice of music, with its use of a now-famous Dropkick Murphys track that is liable to get any Irish person’s blood pumping.

Vera Farmiga had a breakthrough role in The Departed as psychiatrist Madolyn Madden and, while she is now well-known via Bates Motel, for me this will always be her most memorable role. The scene where Costigan goes into meltdown during a therapy session with her is one of the best scenes ever. For many, DiCaprio should have had an Oscar for his role in this film, but he wasn’t even nominated for it (he was nominated for his admittedly impressive turn in Blood Diamond instead). Good job he finally got an Oscar this year so the injustice won’t keep people like me awake at night any more. But even apart from Billy Costigan, the film is full of iconic scenes and characters, benefiting from a great screenplay and one of the best casts ever assembled. The Departed is a truly special film.