The idea of reptilians on Earth was popularized by David Icke, a conspiracy theorist who claims shape-shifting reptilian aliens control Earth by taking on human form and gaining political power to manipulate our societies. Icke has claimed on multiple occasions that many of the world leaders are, or are possessed by, reptilians ruling the world. According to British writer David Icke, 5- to 12-foot (1.5–3.7 m) tall, blood-drinking, shape-shifting reptilian humanoids from the Alpha Draconis star system, now hiding in underground bases, are the force behind a worldwide conspiracy against humanity. He contends that most of the world's leaders are related to these reptilians, including George W. Bush of the United States, and Queen Elizabeth II of the United Kingdom. Icke's conspiracy theories now have supporters in 47 countries and he has given lectures to crowds of up to 6,000.