To mark the 150th anniversary of Berkshire's Broadmoor Hospital, a psychiatric unit for the criminally insane, we're looking at the psychology of some of the world's most dangerous killers. Each week criminologist Professor David Wilson investigates one of the seven typologies of a killer to explain why some people become murderers.
So far we have looked at Hedonistic Killers, Missionary Killers and Mass Killers, focussing on killers Colin Ireland, Fred West and Anders Behring Breivik respectively.
This week we are looking into the minds of killers seeking power and control, focussing on Harold Shipman. Watch Dr Wilson explain what makes a missionary killer