O2 (UK) O2 (UK) Telefónica UK Limited (trading as O2 – stylised as O) is a telecommunications services provider in the United Kingdom, owned by the Spanish multinational Telefónica, and is headquartered in Slough. With 25 million subscribers (as of December 2017), O2 is the second-largest mobile network operator in the United Kingdom after EE, with Vodafone in third place. O2 was formed in 1985 as Cellnet, a 60:40 joint venture between BT Group and Securicor. In 1999, BT Group acquired Securicor's share of Cellnet and the company was later rebranded as BT Cellnet. In June 2000, BT Cellnet launched the world's
The O2 purchased by the mobile telephone provider O2 from its developers, Anschutz Entertainment Group (AEG), during the development of the district. AEG owns the long-term lease on the O2 Arena and surrounding leisure space. From the closure of the original "Millennium Experience" exhibition occupying the site, several ways of reusing the Millennium Dome's shell were proposed and then rejected. The renaming of the Dome in 2005 gave publicity to its transition into an entertainment district. The Dome's shell remained in situ, but its interior and the area around North Greenwich Station, the QE2 pier and the main entrance area were completely