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 (Ireland) Ireland and Three Ireland, offering services in some built-up areas in late 2006. In July 2007, O2 launched its mobile broadband offering in Ireland using HSDPA technology over its 3G network. They provided speeds of up to 7.2 Mbit/s and claimed to cover 90% of the population on the least contended Irish 3G network following an upgrade in 2007. Speak Easy was the name of O2 Ireland's prepaid service. In 2007 they became the first Irish operator to offer free text messages to all Irish mobile numbers, although it only applied for weekends. However, in early 2008 they introduced a