Passing off protects something more concrete than a title: the actual clientele that a sign has built up. It does not ask whether you have registered a trade mark, but whether the public actually associates that sign with you, whether the competitor has misled that public, and whether you have suffered as a result.
It is a heavier action — three elements to prove, as matters of fact — but open to those who have registered nothing. And it has a counter-intuitive consequence for big brands: a worldwide reputation is not enough if the clientele does not exist locally.
McDonald's experienced this in Malaysia, in the dispute that pitted it for eight years against the McCurry restaurant in Kuala Lumpur: the Court of Appeal rejected the passing off claim, noting that the signage, menu and clientele of the two businesses had nothing in common. The Federal Court refused McDonald's leave to appeal in September 2009.