The Helsinki based Mobile Advertising Solution (MAS) has launched 123play.com to their UK customers. The site offers free games for mobile phones made available through advertisements. Since we aren’t in the UK we were unable to test the games. However, Pocketgamer has tested the games and according to their tests, the service works as promised.
Once you enter your profile information, you are allowed to load the games through WAP-links. The user is presented with mobile advertisements that show up in pop-ups on the browser, where you can click yourself to the WAP-sites of the advertisers.
123play.com works as an operator and thus does not provide any games of their own. They provide, according to Pocketgamer, games from THQ Wireless, RealArcade, Digital Chocolate, Hands-On Mobile, and Indiagames.
Thanks to Juhani for the tip!