You'd better hurry though. The offer is only available for a few hours at Green Man Gaming, and copies are probably flying off virtual shelves as quickly as if they had little digital wings and also their bottoms were on fire. Don't forget, Guild Wars 2 has no subscription fee, so if you're interested and in the UK, this looks like a pretty good deal - especially compared to the official ArenaNet prices .
All gone now, sorry!
(Disclaimer: The guy above is not the actual Green Man. Do not give him your money.)