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 The O2 The O2 is a large entertainment district on the Greenwich peninsula in South East London, England, including an indoor arena, a music club, a Cineworld cinema, an exhibition space, piazzas, bars and restaurants. It was built largely within the former Millennium Dome, a large dome-shaped canopy built to house an exhibition celebrating the turn of the third millennium; consequently "The Dome" remains a name in common usage for the venue. It is sometimes referred to as The O2 Arena, but that name properly refers to a smaller indoor arena within The O2. Naming rights to the district were