Pay-TV firm Sky is launching a mobile phone service next year in partnership with O2's Spanish parent Telefonica. Sky will use Telefonica UK's wireless network, enabling the satellite broadcaster to offer mobile voice and data services for the first time. It takes Sky into the battle for "quad play", adding mobile to its existing services of internet, landline and TV. Offering all four services is seen as the next big UK growth area for telecoms firms and broadcasters. Sky already serve 20 million customers in three of Europe's four largest markets.