Nigerian Femi Nandap stabbed Jeroen Ensink to death in Islington, north London, while in a psychotic rage last December. At the Old Bailey he was given an indefinite hospital order.

Dr Trevor Turner, a consultant psychiatrist, explained to the BBC's Eddie Mair what psychosis is and whether it can put those suffering from it, or those around them, at risk.

(Picture: Court sketch of Femi Nandap Credit: Julia Quenzler)