O2 (UK) cent share of Cellnet for £3.15 billion. Cellnet had five million customers at the time of its acquisition. The company was later rebranded as BT Cellnet , and it became a part of BT Wireless, a group of companies owned by BT. BT announced on 3 September 2001 that the BT Wireless business would be spun off from the main group as a newly listed holding company, mmO2 plc, operating under the "O2" brand. Shareholders approved the plan at an extraordinary general meeting on 23 October 2001. BT Cellnet relaunched as "O2" on 18 June 2002, along with other former
O2 (UK) certified with the Carbon Trust Standard in recognition of its commitment to reduce its carbon footprint. O2 attained the standard after saving 47,000 tonnes of carbon over the previous three years through its energy efficiency measures, including a £1.4 million distribution of smart metering technology across the company's cell sites, offices and retail stores, and upgrades to more energy efficient systems across its mobile phone network. In addition to distributing energy efficient LED lighting and boiler system controls, the company was also able to reduce energy use by removing air conditioning units from some of its cell sites and reducing