Sometimes a film comes along and wrong-foots an audience. Occasionally it can do this multiple times. This is the case with Ash Is Purest White, a dense, sprawling drama that initially seems to be a thriller concerning low-level gangsters, before it blossoms into a fascinating and occasionally frustrating look at a changing China over 16 years.

Director Jia Zhang-ke’s latest follows Qiao, who comes from a rundown coal-mining town and is the girlfriend of Bin. Bin is a gangster running a nightclub. They exist in a comfortable harmony until their balance of power becomes threatened. This leads to a gun being fired in a public place and Qiao taking the fall. This is only the first third of Ash Is Purest White, which promptly time-jumps, not once but twice during its (well-over two hour) running time.

Ash Is Purest White benefits greatly from an exceptional lead performance from Tao Zhao as Qiao. There is a lyrical, leisurely pace at play that certainly makes the film an endurance test, yet in Zhao there is a consistent, compelling focus. At times unreadable, at others propelled by a furious determination, it is a performance that lingers long afterwards. Zhao, a long-time collaborator with the director, is the film's greatest asset. But that isn't to say the rest of the ensemble are in any way weak. In particular, Fan Liao (as Bin) effectively represents the complexity of a relatively dislikeable character.

Chinese cinema often feels like it is grappling with the journey the country has gone through in the past quarter of a century, under unprecedented economic development. While Zhang-ke retains much of the focus on Qiao, he uses the broader canvas of his film to explore this transition. From something as small as the mobile phones used by characters, to the broader landscape that goes through massive changes around them, Ash Is Purest White is at its most engaging when it finds the space to explore this topic. It may suffer from a lack of pace and an impenetrable quality, but Zhang-ke's film does have an engaging understanding of modern China.

I managed to lose my footing with Ash is Purest White a number of times during its running time, with the film rarely proceeding as expected. It makes a fascinating, if somewhat frustrating affair, elevated by a terrific performance from Tao Zhao.

This is a London Film Festival preview and Ash Is Purest White will be released at a later date.