London Underground's free Wi-Fi will be available to O2 customers - as well as those on EE, Vodafone and Virgin Media - from this summer.
O2 mobile phone customers are to get free Wi-Fi on the London Underground.
Virgin Media, which operates a wireless network covering 120 of the captial's tube stations, has announced it recently signed up O2 as a wholesale partner for the service.
It means O2 mobile customers will be able to use the free Wi-Fi, staying connected to the internet on their smartphones and tablets while moving around Underground stations.
The service is already available to EE, Vodafone and Virgin Media customers.
Mark Williamson, head of London Wi-Fi at Virgin Media, said: "Wi-Fi on London Underground has gone from strength to strength and we're delighted the majority of Londoners are staying connected at no extra cost.
"Virgin Media's unique fibre optic network means we deliver unrivalled capacity for next-generation digital services both inside and outside the home."
Gary Booker, head of O2's consumer division, added: "We're excited to bring free Underground Wi-Fi to O2 customers this summer.
"Our customers want to stay connected wherever they are and will soon be able to check their email, update their Facebook status, shop online, book their next holiday and stay connected to their friends and family right across tube stations in Central London."
Gareth Powell, director of strategy and service development for London Underground, said: "Wi-Fi on the tube is part of how we're improving services for our customers.
"2013 is London Underground's 150th anniversary - we were at the forefront of technology when the first Underground train ran, and this shows how we are maintaining that tradition, using modern technology to improve customers' journeys."