Some silly cliches and tiresomely obvious liberal-balance contrivances have been pumped into this action-thriller for Netflix from South African director Mandla Dube, which is inspired by one of the most sensational events in anti-apartheid history: the Silverton siege in 1980. Three armed activists of the ANC’s uMkhonto we Sizwe (“spear of the nation”) wing – Humphrey Makhubo, Fanie Mafoko, and Wilfred Madela – occupied a bank in Silverton, Pretoria, after the chaotic abandonment of another operation to sabotage an oil plant, taking 25 people hostage and demanded the release of Nelson Mandela. Meanwhile armed officers grimly surrounded the building.

The movie version turns these three men into two men and a woman, with different fictional names: Calvin (Thabo Rametsi), Aldo (Stefan Erasmus) and Terra (Noxolo Dlamini). In accordance with time-honoured Hollywood practice, the film invents a “good” white cop: Captain Langerman (Arnold Vosloo), a careworn, fair-minded guy who comes to respect the hostage-takers’ idealism. There is also a “bad” white cop, the fascistic brigadier (Justin Strydom), known as “Little Crocodile” in homage to South Africa’s “Big Crocodile” prime minister: apartheid strongman PW Botha. The brigadier of course overrules Langerman’s softer approach.

The movie imagines that there is a police informer inside the ANC group (I wonder what the present-day ANC think about this touch) and it also fictionalises a deeply unlikely government minister’s daughter who actually works at the bank in an assistant-managerial position, and whose liberal views come out in a full-blown and somewhat bizarre Patty Hearst episode. And just in case there aren’t enough stock situations, we get a bit of Butch-and-Sundance defiance as well. It’s pretty routine stuff, and disappointing.

• Silverton Siege is available on 27 April on Netflix.