The film is adapted from Max Brooks’s novel, and Pitt stars as a UN investigator on a global mission to find patient zero in a zombie epidemic. That eye-popping budget buys some mindblowing scenes – the best are skin-crawlingly nightmarish shots of a swarm of zombies over-running a city like truckloads of ants in a garden. But $200 million should have stretched to a third act – set in a laboratory in Wales – that doesn’t look like something you’d watch on BBC4 in the wee hours. And by the end, the pulse of ‘World War Z’ is pretty weak.