Having launched to help visitors to the 2012 London Olympics stay connected on their travels, Virgin Media's Tube Wi-Fi network has become a standard service for commuters and passengers alike over the intervening years. And thanks to deals with the networks, it is essentially a free service to almost all mobile phone users.

Customers of networks EE (including T-Mobile and Orange), O2, Three and Vodafone get free Wi-Fi on the Underground system as part of their contracts, as do Virgin Media broadband and mobile subscribers. But what if you aren't on the major networks? Or you are a tourist or occasional visitor to the capital? You'll have to pay, but by how much?

So where can you get it and how much does it cost? Read on to find out.

What stations will have Wi-Fi?

There are now 150 stations already running Wi-Fi, which Virgin Media lists in a handy alphabetical guide at my.virginmedia.com/wifi/station-guide. Stations most covered tend to be the more central stops, such as Oxford Circus and Liverpool Street, but there are plenty of more-remote ones these days, especially on the major lines.

The latest to have been added to the network are Wimbledon, Richmond, East Ham, Barking, Upminster and Morden.

How can I get Wi-Fi access?

When you first connect to the Wi-Fi service you will be faced with a holding page which gives you several options. If you are with one of the big providers, you will need to log in through their individual section by tapping on the logo. Depending on the network, this will ask for your mobile number and a PIN code that you will have to get beforehand.

EE, for example, asks its customers to send a text to a specific number that will return a PIN code for Underground Wi-Fi access. You should check with your individual network provider to find out the exact process.

Those not on EE, Vodafone, O2, Three or are not Virgin Media broadband or mobile customers will have to buy a daily, weekly or monthly pass. Virgin Media requires you to register first on its dedicated Tube Wi-Fi internet page: my.virginmedia.com/wifi.

How much will it cost?

As mentioned above, Tube Wi-Fi access for those not on the partnered networks or with Virgin Media will need to pay for a daily, weekly or monthly pass. Prices are straightforward. It will cost £2 per day, £5 for a week's access, or £15 a month for a Virgin Media Wi-Fi pass. The company has also added an incentive for longer term customers - a two-month pass is also available for £15, but that's on a "special" basis. We don't know long that will last.

READ: Virgin Media Wi-Fi on London Underground pictures and hands-on

Everyone will be able to access the Virgin Media portal which will list other information such as the latest travel updates regardless of whether they subscribe or not.

Is Wi-Fi anywhere else on London's transport network?

Transport for London also has a deal with BSkyB's The Cloud service to provide Wi-Fi on 56 London Overground stations.