The story falls so squarely into the “truth is stranger than fiction” category that on reading the tagline about an African-American cop infiltrating the Ku Klux Klan, I assumed the film was a comedy.

While there are comedic moments, I couldn’t have been more wrong about the genre. BlacKkKlansman clearly demonstrates why Spike Lee has come to be considered far more than a social commentator – this film is a cleverly disguised piece of political polemic.

It follows the real-life experiences of Ron Stallworth (David John Washington) as Colorado Springs’ first African-American police officer after he is accepted into the department following an outrageous job interview. Initially, the police chief (Robert John Burke) assigns him to the records room but Stallworth has bigger ambitions and so, when offered an undercover assignment, he leaps at the chance.

Unfortunately, the assignment involves betraying his own community by wearing a wire at a meeting where ex-Black Panther and civil rights leader Kwame Ture (Corey Hawkins) is to speak.

Disgusted by the way his superiors view civil rights activists such as Patrice Dumas (Laura Harrier) as dangerous subversives, yet let the rhetoric of white supremacists slide, Stallworth calls a Ku Klux Klan recruitment line advertised in the local paper, passes himself off as white and organises to meet with the local chapter.

Despite handling the majority of the investigation over the phone in conversations with Grand Wizard David Duke (Topher Grace), Stallworth obviously can’t show up in person, so he recruits fellow cop Flip Zimmerman (Adam Driver) to play him at face-to-face meetings with the Klan.

Lee’s depiction of the local Klansmen is a strange balancing act as the bunch of inept, uneducated but seriously well-armed bigots are a source of both comedy and extreme anxiety. In fact, much of the laughter generated by the film is more from nervous tension than mirth.

Stallworth and Zimmerman (who has Jewish ancestry, which means he also “has skin in the game”) both spend the majority of the film a heartbeat away from their deception being uncovered.

Yet the most powerful aspect of BlacKkKlansman is not the tension but the resonances with present-day race relations in America. There are lines of dialogue in the mouths of racist characters that echo current right-wing commentary around the rise of neo-Nazis, the alt-right and condemnation of the Black Lives Matter movement in the US.

If audience members harbour any doubt about the political nature of this film, the final minutes lay their questions to rest. Lee concludes the film with recent footage from Charlottesville, Virginia, and Trump’s subsequent refusal to denounce the alt-right, which was welcomed by national KKK leader and Trump supporter David Duke as “a turning point for the people of this country”.

Lee’s message is clear. It may be 40 years later but not much has changed; the issues remain and the fight continues.