Last modified on Fri 18 Dec 2020 00.18 EST The artist Ai Weiwei is emerging as a ferociously productive documentary film-maker, with two other feature credits just this year: Vivos, about the abduction of protesting students in Mexico, and CoroNation, about the spread of Covid-19 in and from Wuhan. But here is his dynamic and visually stunning Cockroach. Apart from anything else, itâs a spectacular action movie that begins with a shot that had me gasping: a Hong Kong protester on a rooftop is cornered by police and, in an attempt to escape, he tries climbing down the unstable scaffolding on the front of the building, with other protesters at street level screaming their alarm. The result is heartstopping.