Which expression is older: "London Royal Parks" or "London's Royal Parks" ? And why is it Hyde Park and not Hyde's Park?

Solution 1:

To a large extent, this is a matter of idiom.

In Hyde Park, Richmond Park, Greenwich Park and Kensington Gardens, the first words are all place-names.

Hyde Park was enclosed by Henry VIII when he obtained the manor of Hyde from the canons of Westminster Abbey in 1536. Wikipedia

The names of the Parks are their proper names, and it would be almost completely alien to use a possessive. A rather contrived example might be

Greenwich's Park has unrivalled architecture

...but that would only happen if it were to be written by Greenwich Borough Council extolling a local virtue over other Parks. It just isn't done.

With regard to London or London's, it's only used if it's necessary to distinguish the Parks in London from others, in much the same way as the Greenwich example. Either form might be used; it's a stylistic choice.

London's Royal Parks receive more visitors than those outside the capital.
The London Royal Parks ensure that it is the greenest city of its size in the world¹.

There are English place names which include an apostrophe (for example Pratt's Bottom) but the Royal Parks are not among them.

¹London Councils