G4S is a British multinational private security company headquartered in London, England. Originating as the Danish København Frederiksberg Nattevagt guarding business, founded in Copenhagen in 1901, the group was renamed to Falck and merged with Group 4 in 2000 to form "Group 4 Falck". In 2004, Group 4 Falck merged with Securicor to form G4S. G4S became the world's leading provider of security solutions, including 40 embassies around the world, GCHQ in the United Kingdom, and over six British prisons. G4S was controversial for alleged racism against illegal immigrants at UK detention centers, a disorganized handling of the 2012 Olympics in London, its involvement with Israeli prisons, its alleged torture of South African prisoners, its background check failures (including that on Islamist mass killer Omar Mateen), and several labor disputes.