After gravelling around on Horseguards' parade a couple of week's ago, I made my way towards St James's via The Mall and the steps that lead up to The Duke of York column:

I was half way up the second flight when I realised that the surface beneath my feet was/is of the lovely York stone variety. I mused at the coincidence re the duke and the stone.

I also noticed how jolly large some of the slabs are, something I have noticed in other places such as in Marylebone and Covent Garden.

Two of the slabs on the middle landing are definitely bigger than my double bed. My trusty measuring app tells me they are approx 3 metres x 2.4 metres, which is slightly larger than the ones in Central Avenue at Covent Garden piazza.
The slab at the center here also features a little square indentation which might be something to do with the installation process. Wiki's basic info about this landmark says that there's York stone to a depth of almost 3.5metres under the column itself. Wow. Grand indeed.