The fearsome roar of Tyrannosaurus Rex as portrayed in film has left many a cinema-goer quaking in their seat.

But new research suggests the king of the dinosaurs made a far more sinister sound.

For a new BBC documentary, naturalist Chris Packham visited Julia Clarke, professor of Vertebrate Palaeontology at the University of Texas, to test out a the theory that dinosaurs actually sounded more like birds and reptiles, than today’s predatory mammals.

“The most chilling noises in the natural world today come from predators, the howl of the wolf, the roar of the tiger, but experts now doubt that T-Rex sounded anything like them,” said Packham.

Dinosaurs are the ancestors of birds and are closely related to alligators and crocodiles, so Prof Clarke used the sound of the Eurasian bittern, which makes an unearthly booming call, and the vocalisations of Chinese crocodiles to estimate the noise T-Rex would have made.