It went live in June, ahead of the London 2012 Olympics. But unlike that event, free Wi-Fi on the London Underground isn't a short-lived affair.That was the original intention though, at least for people not on the Virgin Media network. But the company has now announced that the network will remain free until the end of the year at least, which is good news if you enjoy catching up with your inbox during the daily commute.What happens after that isn't clear right now. The idea is to offer the service free to anyone signed up to Virgin Media's broadband or mobile services, with the rest of the mobile population looking at paying for use of the service. But as this system has yet to be finalised, the service remains free and is likely to until Virgin sorts all of that out.There is a chance that Virgin could offer network access to other companies, who in turn could offer it to customers either as a free add-on or on discounted terms. It would certainly be a selling point for the networks, especially when flogging phones in the capital. Watch this space about that one, as it's a possibility next year.But if the worst case scenario does come into effect, you might have to pay for access if you need it, although access to TfL details and some information on the city will remain free to all Tube users.