In message , Dik T. Winter writes

In article Mark B
writes:
Which is right,
St James' Park (on the signs)
St James Park (in the FGW Timetable)
Pronounced St James's Park, both locally and on the AutoAnouncer

I think you never will know which is right. If I remember right, there
are Earl's Court and Barron's Court, both with and without apostrophe.
LT uses the apostrophe in one of them, the street signs use it on the other.

Exactly. When it comes to place names, their form is dictated by
historical precedent and custom rather than rules of grammar.

For instance, in Elizabethan times, travellers from the north would most
likely enter the city through "Bysshopes Gate". Despite the fact that
the standard genitive ending ("-es") indicates a possessive noun, it was
never modernised to "Bishop's Gate" or even "Bishops' Gate" - instead
(and as early as the 17th century) it became simply Bishopsgate.

--
Paul Terry