Cellnet

Formed on 7 January 1985 as Cellnet, a 60:40 joint venture between BT Group and Securicor. Cellnet was one of the first two mobile networks in the UK. In 1999, BT acquired Securicor's share of Cellnet and the company was later rebranded as BT Cellnet. This was spun off from the BT Group in 2002 to form a new holding company, mmO2 plc, which introduced the new "O₂" brand for the businesses. O₂ plc was purchased by the Spanish telecommunications company Telefónica in 2006 for £18 billion. On 1 June 2021, O2 and Virgin Media formally merged to create Virgin Media O2