A stone at 345 Gray’s Inn Road, London. Long thought to be an old milestone the Ordnance Survey map of 1868-73 (https://maps.nls.uk/view/102345964) shows it as a milestone marking 1 mile to Holborn.
There is a short article on it here by Ian Visit:
https://www.ianvisits.co.uk/blog/2019/03/28/find-the-kings-cross-milestone/
I hoped that photogrammetry might reveal some hard to discern inscription but none is visible to my eye unfortunately.
65 photos taken in June 2019 with a Sony a6000 and processed in Agisoft Metashape.