Turkey
Veg, which should probably be parsnips, brussel sprouts, carrot, mashed swede.
I do know a lot of people are fond of red cabbage, but it's usually a bit sweet for me by the time it's been messed about with, and almost no one ever serves plain red cabbage. Also not fond of cauliflower cheese, though plain cauliflower is fine. Peas, cabbage, broccoli, green beans also all acceptable. Vegetables are essentially a vehicle for soaking up gravy, and a variety should not all be root vegetables or all be brassica or all be legumes, though if seasonal, roots and legumes will predominate.
Roast spuds. (Essential for any roast. You can’t do too many roast spuds.)
My mother always served mashed potatoes as well, though that seems unnecessary to me (though I sm generally a fan.)
Gravy. (Essential for any roast.)
Bread sauce (we had none.)
Cranberry sauce (we had none.)
Pigs in blankets (we had none.)
At least one type of stuffing. We had one with dried apricot, parsley and breadcrumbs, which was okay, but a good sage & onion sausage meat stuffing is traditional. Mum always did a chestnut based one as well, that may have involved giblets in some way, but I'm unsure of the details. (The giblets ultimately ended up being fed to the cat, but I think they made stock first.)
I was a bit disappointed by our Christmas Dinner, because while it was excellent, it did not include all the trimmings. Obviously I have not said so out loud. But I may have to rectify it once I'm back home, because I really like a proper Christmas dinner.