Even if he thinks he's safe, he may not be. There IS legislation in British law which would provide (if the UK ever used it) for the Embassy to lose its status as one, in which case, the Embassy would become British soil, therefore fully accessible to our authorities.
This is problematic, though, because if the diplomatic inviolability of foreign Embassies was brought into question more generally, the effect worldwide could be potentially ruinous.
My guess - Westminster will wait .. for a while. If they become convinced that this is too unbreakable a stalemate, though, they will revoke the status of the Embassy and go in to take Assange into custody. I don't believe we'll wait 'forever' before acting.
http://hereandnow.wbur.org/2012/08/1...lemate-embassy