That's what the original Johnston apostrophes look like.
snip

Sorry, I know what both the Johnston and New Johnston typefaces (and
the apostrophe's) look like... this is most certainly neither of the
two.

it looks like the traditional "round ball with hook" type to me

I see what you mean. The "St. James' Park" sign is in a typeface that is
close to but not identical to either Johnston or New Johnston.

As you say, the apostrophe has a circular ball at the top, but the dot
under the T of "ST." is square. Also, several letters are narrower than
Johnston, and the E and K have subtly different proportions. Looks like an
amateur attempt to copy Johnston. I wonder why.

[Michael: I have photos of the signs. Email me (see sig) if you want
copies.]

Perhaps Gill Sans?
http://www.adobe.com/type/browser/F/...10005000.jhtml

I know either Johnston or Gill Sans was based on the other, and it has
similar looking Upper Case chars, and the correct apostrophe.. what do
you think?

Michael