The hottest chilli pepper in The Guinness Book of Records is a Red Savina habaņero with a rating of 570,000 Scoville Heat Units (SHU).

Mrs Michaud was stunned when the Dorset Naga gave a reading of nearly 900,000SHU. A fresh sample was sent to a lab in New York used by the American Spice Trade Association and recorded a mouth-numbing 923,000SHUs.
I always thought that you yanks had the hottest.Beaten by the poms eh..