O2 was born in 2002, a relaunch of the former BT Cellnet. Today, O2 is a completely different animal to its troubled predecessor. In December 2005, it overtook Vodafone to become the UK's leading mobile phone operator, with 16 million active customers. In an increasingly commoditised market, O2 has successfully stood out from the competition with an award-winning marketing strategy that has not only made existing customers more loyal but also helped it acquire more new users than competitors. In January 2006, the success of the O2 group was reflected in the £18 billion paid for it by the Spanish telecoms group, Telefonica.