So I finally found a reference to the jacket and tie rule....on page of the hotel brochure. Perhaps a quick mention on the main restaurant page would be helpful. Plus, that still doesn't explain why the rule was only enforced upon us, rather than the other men in the restaurant last Friday.
The jacket and tie rule was requested in the a la carte restaurant but the same a la carte menu is offered under the awning outside (with heaters) where the dress code is less strict.
However I am sure these guidelines are less strict these days.
Get an answer from The George Of Stamford staff and past guests.