I think there is something a little odd about the background...if those are the Hampton Court gates, which they certainly do look like, then where has that very tall stone wall on the left gone to? Unless it was bombed/pulled down I suppose?
But..where has the long horn of the unicorn gone?
If you look closely at the tree line above the actual gates..it looks as if it has been cut out and superimposed.
But most of all, below is a photograph of the Trophy Gates, taken between 1850 and 1870..showing a substantial building in the place where there appear to be huge trees...and in modern photos, the building is still there..is it possible the original picture has a touch of artistic-poetic licence?