O2 (UK) BT subsidiaries: Esat Digifone in Ireland, Viag Interkom in Germany and Telfort Mobiel in the Netherlands. The rebranding was supported by a European advertising campaign, which began on 16 April 2002, across all four countries, at a cost of £130 million. The main launch campaign ran from 18 June and was developed by Vallance Carruthers Coleman Priest, working alongside brand consultancy Lambie-Nairn, creators of the "O2" brand identity. In March 2005, mmO2 restructured its shares and the company was relisted as O2 plc. On 30 November 2005, O2 agreed to a takeover by Telefónica, a Spanish telecommunications company, for £17.7
The O2 in 2006. As part of the investment programme, naming rights were sold to O2 plc, and 'The O2' became the official name of the project on 25 May 2005. The £6 million per year deal between O2 plc and AEG included priority tickets and reserved VIP accommodation for O2 mobile customers. The service was also made available to premium ticket holders. O2 plc started talks with AEG in 2005 to have its logo and branding placed on the roof of the dome, but this did not take place. AEG have constantly stated that they wish to abolish the 'Dome' name