O2 (UK) they can do it too" in reference to Vodafone and EE, O2's biggest competitors and the UK's top three mobile-telecoms companies. 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
O2 Money application for Android and iOS devices. The application will use NFC technology embedded in a phone to access money banked with Barclays via O2. O2 began trials of NFC technology in , with 500 individuals participating in the trial. The individuals used a specific Nokia handset to make payments at selected retailers, and travel the London Underground with transactions made via Barclays. O2 has since been in discussions with large retailers, such as Tesco and W. H. Smith, for the deployment of the necessary electronic point of sale units, and with handset manufacturers, such as Apple and Samsung, to enable