145 million years ago an adolescent Allosaurus lay down to die in a dried up river bed. In 1991 scientists discovered his perfectly preserved body and nicknamed him Big Al. This is the story of this predatory dinosaur's life - how he grew from a tiny hatchling to the terror of the Jurassic plains, why his body was covered in so many wounds and how he ended up in the river bed. The second part tells the story of the extraordinary forensics, spectacular paleontological finds and intricate studies of Al's closest living relatives to unravel his intriguing life for the film.

• Kenneth Branagh