A career studying dinosaurs is surely spent au fait with unhappy endings. Even so, anger hangs over Dinosaur 13, a documentary about the place where science meets the profit motive and the US legal system is at its most palpably crackers. Trouble brews in 1990 as a band of geeky palaeontologists in South Dakota stumble on a near complete skeleton of a Tyrannosaurus Rex. But before the museum gift shop can print the tea-towels, the bones become subject to an acrid custody battle. It’s hard not to end up watching as if sitting with the disinterred T-Rex, looking on in cold silence at its squabbling inheritors.