O2 (UK) Telefónica O2 had a long-standing relationship with Arsenal F.C., being their shirt sponsor until the end of the 2005/2006 season. In 2005, a three-year deal was signed that saw Telefónica O2 become the team's exclusive mobile communications partner. O2 were the main sponsor of the Channel 4 reality TV show "Big Brother" from its second series (as BT Cellnet) in 2001 until its fourth series in 2003. They also sponsored the spin-off shows "Celebrity Big Brother 2" in 2002 and "" in 2003. In total O2 sponsored five series of the show. O2 sponsored music festivals, the Wireless Festivals, from
O2 Czech Republic different lines of business: the retail operator O2 and the wholesale infrastructure provider CETIN. The separation includes commercial and managerial leadership and management of both companies, including security, IT and control systems. The company was initially known as SPT Telecom ("Státní telekomunikační podnik", state-owned telecommunications company), and used to have a monopoly for providing fixed-line services. It was reorganized and renamed Český Telecom (Czech Telecom), after the Velvet Divorce saw Czechoslovakia separate into the Czech Republic and Slovakia in 1993. Its mobile subsidiary, Eurotel, was founded in 1990 as a joint venture between SPT (51%) and the American joint-venture Atlantic