Oh what a mix-up !

There are 3 Parks, St James, Green and Hyde Parks. St James (flowers, trees and bushes, big pond, ducks, even a couple of flamingos) is the one in front of the front door of B.P., Green Park (trees but otherwise a bit bare) is to the left, and Hyde Park (very) peripherally just comes up to one corner of the back garden of the palace, then stretches well to the west, and is far and away the biggest one, with a very big pond indeed.

Stables are in Hyde Park (only one you can ride in). Churchill Museum in the Horse Guards at the opposite, east end of St James Park to B.P. Speakers Corner at north-east corner of Hyde Park (aka Marble Arch). Harrods under the south side of Hyde Park but not really close to it.

All 3 have Underground stations named after them. St James Park is a few minutes walk away from the south side of its namesake, Green Park is immediately on the north of its owner, and Hyde Park (Corner) is at the south-east corner of H.P.

For management they are all under the Royal Parks organisation, but there is much friendly, and occasionally stronger (!) rivalry between the staff of the three.