Kings Road or King's Road? Which is correct for the trendy Chelsea thoroughfare?

Well, it gets its name from being the road built for the King (King Charles II to be precise — more on that here).
So by that reckoning, the road belongs to the King and should have the possessive apostrophe, making King's Road (or the King's Road, if you prefer) correct.
The message doesn't seem to have got back to the signmakers though, judging by the variety of signs that appear on the street:



Similarly, Google Maps seems to contradict itself. The road itself is King's Rd, but the branches of chain stores such as Pandora and Nike appear as the apostrophe-less Kings Road.

Even the brands themselves don't seem sure. On their own websites, Pandora opts for Kings Road while Nike goes with King's Road:

But trust us — King's Road is right.
See also: Should King(')s Cross have an apostrophe?