The acclaimed Palestinian cartoonist was gunned down in London in 1987. His attackers have never been identified. Naji al-Ali's cartoons were famous across the Middle East. Through his images he criticised Israeli and US policy in the region, but unlike many, he also lambasted Arab despotic regimes and the leadership of the PLO. His signature character was called Handala - a poor Palestinian refugee child with spiky hair, who would always appear, facing away with his hands clasped behind his back, watching the events depicted in the cartoon. Alex Last has been speaking to his son, Khalid, about his father's life and death.