There's one in the grounds of Knebworth House, which I've seen. I think the top photo is of it - I remember the plaque.
Ashton Court, on the other side of the Clifton Suspension Bridge, Bristol, has several. No doubt carefully nurtured for over a hundred years from seeds or seedlings. And then, some bright sparks involved with the upkeep of the woodland there decided to cut half of them down. There may have been some genuine problem with diseased trees behind this, but judging by the brainless - but apparently authorised - tree felling all over the Bristol area, I wouldn't bet on it.
