Says who? Sweden? The UK? Assange? The US?
The "special relationship" is not a cover-all term for the US & UK to do anything on a promise like a teen couple in love. It covers a lot of military and trade stuff, which wikileaks is a part of, but in this case Sweden clearly acted as a player in a larger game. Assange seems to have presumed an ulterior motive in the charges brought against him and proceeded accordingly.