JAMES MARTIN has a special restuarant on OV1 and OV2, these are usually booked as soon as you board, they will have a display and person ready to take your booking. (you can see details on OV web page). Sister in law had a great 80th birthady celebration in there on OV2. Have a great time, we always do .
Normally when I make our booking I advise we have a special celebration and usually during dinner a cake arrives after the meal is over and the waiters in about 5/6 dialects sing Happy anniversary you can also book a meal in the special restuarant if OV has this, don't know as I have never travelled with them but perhaps someone will advise you further, but food for thought !!
I agree with PLAIN, although we were not lucky enough to book the Jame Martin restaurant, i would recommend it as everyone who did were very pleased with the food and service, although i would recommend that you book a table as soon as you board the ship, as our rep asked us when we went to a meeting at our hotel and assured us that he would take care of the booking for our 25th anniversary but unfortunately he forgot. Just join the queue, if you speak to you tour operator you should be able to find out if James is sailing and you will get a chance to have your meal prepared by himself.