We will be in London over Christmas and have enjoyed Christmas dinners on previous visits, all within walking distance of hour hotels. We will be staying near Trafalgar Square this time and will need to walk to venues within a 30 minute walk. I know it's a bit early for schedules to be out but any advice or previous experience on Christmas Day would be most welcome.
We stayed at The Trafalgar Hilton Dec 2014 and ate Christmas dinner there-it was not a big expensive production.
Hawksmoor on Air Street, at the bottom end of Regent Street is a 5 minute walk from Trafalgar Square and is excellent. Surprisingly, Christmas menus don't seem to be out yet.
it's a bit early for schedules - not by much, things should be happening soon, these get sold out very quickly. Be aware that traditionally LUNCH is the main meal on Christmas Day (although it may be served mid afternoon), if you only search for evening availablity the list will be shorter.
Malmaison Hotel has already published their christmas season programme, although they are slightly beyond your walking limit. And the price is a bit eye watering.
https://www.malmaison.com/media/3201977/mal-xmas-a5-london-brochure-2017.pdf
what about the place you are staying at?