Today's the day that your cost-free tweeting about red signals comes to end, as Virgin Media begins charging for its WiFi service on the London Underground. If you're a Virgin, Vodafone or EE customer, then you just need to sign up to continue getting access as part of your mobile plan. For everyone else, avoiding getting your fingers sticky on that day's issue of Metro will cost you £2 a day, £5 per seven-day week or £15 a month. If you take up the latter option at any point in February, you'll be given an additional sweetener: three months for the price of one. The company has also announced that Hampstead, Tooting Broadway and Great Portland Street are among 11 more stations that are due to come online this week.