Jane Lumley writes:

Okay, joke over, but the rationale Tony Lord gives is that it extends
the display - fine, but is the goal of the N Trust to preserve, or
merely to give the punters what they'd get in the local park? What do
others think? I get depressed when I see historic gardens tarted up,
like seeing the Mona Lisa restored with acrylic paint because that's
what visitors now want.

I agree with you.
I would have thought the goal of an "historic" garden is to preserve history.
If not, then why use an estate? Just plant them in any park.