Knut died of illness never previously seen in animals
The mystery surrounding the death of the famous polar bear Knut, who died at Berlin Zoo in 2011, has finally been solved.
Millions of people were shocked when the four-year-old bear was found dead in the moat of his enclosure after suffering a seizure.
A new investigation has shown that he had a type of autoimmune inflammation of the brain that is also recognised in humans.
Tim Allman reports.