Windsor Castle tickets, where to eat in Windsor

No it isn't necessary to purchase tickets in advance. There is a great pub
Horse and Groom, which is across the street from the Henry VII gate which you exit the castle from. Edited: Laurel is right, I should have mentioned the Crooked House.

Also the Crooked House tho some may think it's a bit over priced

Thanks so much for sharing your information on Windsor! It's great to have a personal recommendation for lunch. Sue

We had lunch at the Horse and Groom last month. It's huge and sort of barnlike, with a cavernous downstairs and a big upstairs. I recommend upstairs. Get a booth by the window, so you can see the big corner tower of the castle as you eat! It can get slammed with tourists - but it still manages to be charming and produce food that is more than edible. And it's just steps from the castle, so it's very convenient. Also recommended - walk into Eton after your've toured the castle. It's a lovely stroll, and the high street in Eton is completely adorable and charming. We had a pint at the Crown and Cushion, which is small and cozy and quaint. (Edit: if you Google the Crown & Cushion you'll see that it apparently closed just before Christmas, but was to re-open under new management. And apparently it did, because we were there at the end of January.)