Call of Duty: Modern Warfare 3 on sale for £60 at Computer eXchange in Rathbone Place, London. Photograph: Guardian Gamers willing to pay above the odds can get their hands on an early copy of this year's must-have game, Call of Duty: Modern Warfare 3 – if they're willing to pay £60, rather than the £35 it costs online. The games were on sale at least 48 hours ahead of the official embargo, which lifts at midnight on Monday, at Computer eXchange in London's Rathbone Place. Shrinkwrapped copies of the games for both Xbox 360 and PlayStation 3 were available in the window at the comparatively high price. Video games stores are expected to open their doors just after midnight on Tuesday morning to satisfy gamers who will have been queuing outside for hours to buy their copies as Modern Warfare 3 officially goes on sale worldwide. But London gamers have been able to buy them from the Computer eXchange chain of stores. When The Guardian's journalist quizzed a shop assistant about the fact that the games were on sale ahead of the worldwide embargo – which publisher Activision has fought hard to maintain, forbidding publications and bloggers from posting reviews online ahead of the release – a shop assistant said that the game was "already on sale in Europe". This however is incorrect. The Guardian believes that Computer eXchange may have acquired advance copies from a European distributor. Computer eXchange declined to answer The Guardian's questions over the phone about where it had got the copies and why it was selling them ahead of the embargo. It requested that questions be sent by email – but had not responded by the time it was told this story would be published. The games industry loves to exercise fine control over when its products go on sale to generate the maximum impact at launch. But its plans are often thwarted. The logistics of getting millions of copies of a game to shops around Europe while ensuring that none go on sale prematurely are fearsome. So while the industry frowns on such practices, it is effectively powerless to plug every single potential leak. In the past, legitimate retail sources have started selling games early before pleading that they made a mistake – such as Argos, which got in trouble for selling 2007's Call of Duty: Modern Warfare 2 before it was supposed to. Mail-order outlets often dispatch pre-ordered games when they receive them, often before the games are officially on sale, so they are often favoured by gamers seeking to get their latest fix before anyone else. C&VG reports that US retailer K-Mart broke ranks to sell copies of Modern Warfare 3 earlier than it should have. One way in which such practices are discouraged is for companies running online gaming services – especially Microsoft with Xbox Live – to collaborate with games developers and publishers and to ban those found playing games online before their official launch date. But distributor Activision said in a statement that "we don't plan to ban players with early legitimate copies of Call of Duty: Modern Warfare 3". With millions of copies of the game pre-ordered, the amount of units that have leaked onto sale early is comparatively insignificant. In practice, publishers turn a blind eye to the practice – as long as it concerns only legitimate, as opposed to pirated, copies of the game. And it could also have pointed out that we're in the middle of a credit crunch, so waiting for the official launch before buying a game can only save you money.