“Everyone knows who won. But not everyone knows how,” says a balding Benedict Cumberbatch in the trailer of HBO’s Brexit, a behind-the-scenes look at the June 2016 referendum in which Britain voted to leave the European Union.

Cumberbatch stars as Dominic Cummings – described in the trailer as the “man behind Brexit” – who headed the Vote Leave campaign that narrowly won the referendum (51.9% voted to leave). The trailer shows Cummings’s cunning as he develops a strategy that taps into voter anger and ropes in hot-button issues such as immigration, race and nostalgia for Britain’s old glory. “We have to hack the political system,” Cummings says. “I’m talking about altering the matrix of politics.”

Co-produced by Channel 4, the film reveals “the personalities, strategies and feuds of the Leave and Remain campaigns”, according to HBO’s official synopsis. “The tactics employed employed by Vote Leave during the data-driven campaign swayed a historically silent voting bloc that would ultimately decide the outcome of the referendum, as well as affecting future elections around the world.”

Directed by Toby Haynes (Doctor Who, Sherlock, Black Mirror), the film also features Rory Kinnear, John Heffernan, Liz White and Richard Goulding in key roles. Brexit will be premiered on January 19, 2019, on HBO.

Brexit (2019).

The trailer has sparked some controversy on social media, Vox reported. Some have expressed concern that the film will glorify Cummings and the divisive Leave campaign, while others have contended that an issue whose ramifications are still playing out should not be adapted to film in such a contentious period.