You Learn Something New Every Day

Walking through the centre of Kingston on Thames today, we noticed this block on a rather nicely carved plinth - and were amazed to learn that it is the coronation stone of the Saxon Kings of England.  Ethelred the Unready sat here!

So, if they already had one, why did Edward 1 need to 'borrow' the one from Scone? This one looks rather more comfortable (I didn't climb over the railings to try it).  

Wiki says it was sort of mislaid, and for a while was used as a mounting block. Maybe they should move it to Westminster Abbey, now that the other one has gone back to Scotland?