Mass murder is awful enough. But some serial killers not only embark on slaying to slake their perverted pleasures but enjoy the mutilation of their victims bodies and sometimes also revert to cannibalism. The simple act of slaying would sicken most people. Yet that is not sufficient a thrill for those who find the excitement begins once their victims are dead. Cutting up corpses is, of course, one way of disposing of the evidence. But here we examine the butchers who dismember for pleasure. They are monsters like Andrei Chikatilo, the so-called Rostov Ripper, who tortured, murdered, chopped up and sometimes cannibalised as many as 50 victims. Or they can be quite unassuming perverts like Dennis Nilsen, whose London house of horrors so overflowed with body parts that they blocked the drains. There is nothing new about this, the sickest side of homicide, of course. The most famous serial killer of all was Jack the Ripper and butchering maniacs have been slashing their bloody path through history ever since. AUTHOR: Nigel Blundell is a journalist who has worked in Australia, the United States and Britain. He spent 25 years in Fleet Street before becoming an author and contributor to national newspapers. He has written more than 40 books, including best-sellers on crime and royalty. He co-wrote the Top Ten expos Fall of the House of Windsor, which first revealed the so-called Squidgygate tape and the infidelity of both Princess Diana and Prince Charles. His other factual subjects have included military history, celebrity scandals, and ghosts and the paranormal. 32 b/w illustrations