Up until 1990, only 12 fossils of Tyrannosaurus Rex had been recovered, the best being 40% complete. The one miraculously preserved in the badlands of South Dakota Hills was 80% complete and a scientific marvel.

So Sue, as she was fondly named by her enchanted liberators, was number 13 – unlucky for some. The following 10 years, which saw their eureka had turned to Kafka, stand testimony to that.

In this impressively mounted and moving documentary director Todd Douglas Miller tells the story in two parts.

The first is mostly geology and paleontology. How Peter Larson and his small but dedicated team from the Black Hills Institute found, and freed, this remarkable specimen.

Their breathless excitement is tempered by infinite patience as the team dig down through 30ft of cliff to get to their fossils and how, with brute force and delicate brushing, they cut her out and transport her to their tiny museum where the small community takes Sue to their hearts.

Peter, says one co-worker, was in love with Sue, and even his wife – a journalist who went to cover the story – acknowledged that he would sometimes just go to talk to the lumbering old box of bones.

Into this heady, naive world of pure, untainted scientific discovery comes – bam! – the heavy boot of Federal Government. 

The FBI and National Guard turn up at their shacks and seizes Sue, claiming theft. Amid the screams of protest from school children and the tears of the scientists, they stick Sue on lorries and put her into storage as a complicated legal battle ensues over ownership.

Although Black Hills had bought the fossil from landowner Maurice Williams, Sue was in the wrong place at the wrong time. The land was overlaid with all sorts of complex legal issues relating to Native Americans and trusts and federal involvement.

Sue had woken up in a very different world.

The second half of the documentary is occupied with this legal battle where bad decision was piled upon injustice until the authorities cornered themselves into taking the most ridiculous punitive action as the only way to justify their initial crassness. “The Government went nuts,” says one participant.

The scientists were punished, traduced, frustrated and kicked – left fighting, even, for their freedom – but they felt they could endure any ordeal as long as Sue was safe and had some kind of future inspiring awe and love.

Talking to the key players now and intercut with contemporary footage, Miller manages to evoke the adrenalin of those days. 

They look back at this chapter – closed when Sue sold for $7.5million to the Field Museum in Chicago – as their high point, when their lives were at their fullest and their every move had pith and significance.

In Miller’s hands, and thanks to the remarkably engaging protagonists, a documentary about an ancient fossil manages to say something significant about our times.

Go to sundance-london.com

Dinosaur 13
(tbc) 105mins
★★★★✩