This collection will tell you about the Mafia's most influential world, their activities and their sources. It looked very interesting. Click On Image For Preview 10. Jamaican-British Yardies Jamaican-British Yardies were the Jamaicans who immigrated to Britain in 1950s. They were involved in gang violence and got to be known as Yardies. They conduct organized crimes like drug trade and other gun crimes. They haven’t tried infiltrating the law enforcement system so they aren’t considered ...