Morris spent three years researching the project , speaking to terrorism experts , police , the secret service , and imams , as well as ordinary Muslims , and writing the script in 2007 . In a separate interview , he asserts that the research predated the 7 July 2005 London bombings : Morris suggested in a mass email , titled " Funding Mentalism " , that fans could contribute between £ 25 and £ 100 each to the production costs of the film and would appear as extras in return . Funding was secured in October 2008 from Film 4 Productions and Warp Films , with Derrin Schlesinger & Mark Herbert producing . Filming began in Sheffield in May 2009
7 July 2005 London bombings
7 July 2005 London bombings
Four Lions