The vast majority of the 1.6 billion Muslims in the world are Sunni, according to a 2009 study by the Pew Research center. Between 10% and 13% are Shia Muslims, and 87% to 90% are Sunni Muslims.

Britain has an estimated Muslim population of about 2.8 million. Of these some 5% are Shia, the rest are Sunni. The historical split occurred 1400 years ago, following the death of Muhammad in ...