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 (UK) as were all the group's other businesses (other than Manx Telecom). The re-branding was overseen by the Lambie-Nairn design agency, which developed the idea of the company supplying services that were essential, much the same as oxygen is essential for life. The company logo and associated graphics were designed using air bubbles to present this concept. The bubbles were photographed by London-based photographer Jonathan Knowles. O2 adopted the slogan "See what you can do" in 2002 after the company's demerger from BT. The slogan was later changed to "It's your O2" in May 2006, on 10 April 2008 to "We’re