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 (Ireland) also run the network operations for Three Ireland"). The Network team outsource was limited to the Field Operations team along with some other support functions. The Network rollout team & Transmission team remained in-house to facilitate future network changes. It was more cost effective to retain these divisions in-house. In 2006 O2 chose Irish Autism Action as their charity of choice. The three-year deal involved sponsorship, creating awareness, using O2 staff to assist the charity and using technology developed by O2 to assist children affected by autism. In 2010, the company's charity of choice became Headstrong, a charity providing mental