In the early 1970s, Ron Stallworth (John David Washington) becomes the first African-American detective in the Colorado Spring police department. Posing as a white supremacist, he makes contact with the local Ku Klux Klan branch. When they offer to meet him personally, Stallworth teams up with colleague Flip Zimmerman (Adam Driver) – a white Jewish member of the vice squad – to infiltrate and investigate the KKK: Stallworth posing over the telephone, and Zimmerman doing it in person.

BlacKkKlansman is one of the best American films of 2018, and a much-deserved mainstream smash for director Spike Lee. Lee is a stalwart of American film, but despite the occasional commercial hit his work – which focuses primarily on issues of race and the African-American experience – usually flies under the radar with audiences. That is a near-criminal shame, since he has been consistently directing and producing some of the USA’s best independent filmmaking. He all-but knocks things out of the park with BlacKkKlansman. The film is based loosely on true events, and comes back with an even balance of drama, thrills, and superbly pitched comedy.

The film is dominated by uniformly strong performances, led by John David Washington as Ron Stallworth. He brings a wonderful idealism to the character, as well as a realistic sense of conflict: race relations in the USA has often been dominated by conflicts of black people versus white police officers, and Stallworth awkwardly straddles that divide as a black police detective. He makes his character enormously likeable, and shows off a great range of emotion as he faces racism directly and on a daily basis. His performance papers over what is perhaps the film’s most troublesome element: making the hero of the story a police officer when African-Americans have faced so much violent opposition from police over the decades. Filmmaker Boots Riley noted and criticised this element of the film last year, and it is easy to see why. As a white viewer of the film I can tread the balance fairly easily, indeed it adds complexity to the character, but for anyone who has actually faced overt racism from police officers may find it a tougher aspect to watch and accept. To Lee’s credit, Stallworth’s job is openly criticised by other African-American characters – notably activist Patrice Dumas (Laura Harrier), with whom Stallworth forms a romantic relationship.

Adam Driver, who is coasting on a wave of excellent performances, shapes Flip Zimmerman as a perfect foil to Stallworth: less openly funny, but as a Jewish character he can provides an alternate view on bigotry in America. The character is fictional – the real-life office has understandably never been identified – but well-developed and realistic. I’m not sure there was a stronger balance of lead actors in a film last year than Washington and Driver; certainly I don’t recall seeing one better. In Driver’s case the performance is particularly impressive as he is tasked with playing not only Zimmerman, but Zimmerman pretending to be a white racist Ron Stallworth. He plays these nested characters to perfection.

The film balances itself between ridiculing the Klan and recognising the terrifying repercussions of what they say and do. It is difficult subject matter – particularly in what is essentially a populist crowd-pleaser – but Lee navigates it with the steady hand of a master filmmaker. Despite this, the provocateur in Lee regularly makes his presence known. The film’s denoument, which generated some controversy upon release, is a violent slap in the face to any viewer who falls into complacency during the upbeat climax. This is a commercial hit that makes its audience think, and more importantly to actively engage with racial violence in America – both historically and in the country today.