It's tradition for the Royal Family to be out in force on Christmas Day for their annual public walk to church.
But the rest of their festive celebrations take place in private behind closed doors on the Sandringham estate.
It's long been rumoured about what they get up to, from exchanging presents on Christmas Eve to having a traditional Turkey lunch and even playing a game where they weigh themselves to check how much of a good time they've had.
But now a former royal butler, who worked for King Charles and Queen Consort Camilla, has opened up about what he heard goes on behind the scenes at Christmas.
Grant Harrold worked at Charles' Highgrove estate for seven years - and although he never went to Sandringham with him, he heard all about some of the traditions that went on there.
And here he reveals what really happens over the festive season...
Festive decorations - and late Queen's tradition
No doubt Sandringham will be decked out in Christmas decorations to really make sure the royals get into the festive spirit.
There will be trees, Christmas wreaths and holly - but according to Grant, th ere is one festive decoration that you will not find in royal homes.
He told the Mirror: "They don't overdo it with the tinsel.
"Everybody gets the tinsel but if you go to a royal home, it is a lot more greenery, baubles and lights, not tinsel."
And to prove his point, when Camilla invited children to Clarence House earlier this month to decorate the Christmas tree - there was not a piece of tinsel in sight.
Meanwhile, Grant also said that when it came to decorating, the late Queen had a very sweet tradition that she would get her grandchildren and great-grandchildren involved in.
He added: "I heard that at Sandringham, the Queen used to arrange for one of the trees in one of the rooms to be left bare for the kids to decorate it.
"It was a tradition that she started and the grandkids would come in and they would all do a bit of decorating, which I thought was always quite a nice idea."
Gift exchange and 'serious' presents
It's long been known that the royals exchange fun, cheap gifts with each other on Christmas Eve - rather than on Christmas Day itself.
This gift exchange is said to take place around 6pm after they enjoy afternoon tea - and in charge of proceedings used to be the late Prince Philip.
But according to royal butler Grant Harrold, who worked for Charles and Camilla for seven years at Highgrove, it may not be the only royal gift exchange of the festive season.
He believes Prince William and Kate always give each other serious presents too - and that the children Prince George, Princess Charlotte and Prince Louis also get their goodies for Santa Claus on Christmas morning - just like other kids.
Speaking to the Mirror, he explained: "With the actual Christmas presents, I've been told they give fun gifts because what do you give a royal who's got everything?
"But I also believe they also give each other nice gifts because even though they do the fun thing, the younger royals for example like William and Catherine, will give each other nice gifts to each other at Christmas, I have no doubt about that at all.
"I also like to think that on Christmas Day the kids will have Father Christmas come and they will get traditional presents under the tree, I think that's probably when you will find that's when the serious presents will be given to each other.
"And I do think they give serious things but unfortunately I don't know what unless we maybe see Catherine wearing some new jewellery or something like that.
"When I see her in a new necklace or something, I often wonder if it's a Christmas gift but we never really know unless they tell us."
Parcels for the staff
Grant also revealed the gifts royals buy their staff - and the jokey presents he received from his boss the now-King.
He said: "At Christmas, we would always get the famous Christmas card. Before he was married to the now Queen Consort, I remember getting Christmas cards from him, William and Harry and that was always quite special.
"The other thing he used to do is, we all used to have these pigeon holes where I'd get my post in the mornings and what he used to do at Christmas, he used to leave funny little things.
"One time he left a tin of salmon and one year I got a salt and pepper grinder wrapped in a ribbon. He had probably been given a hamper and sometimes there would be a lot in them and he would give some of the bits to us.
"I just thought it was so bizarre because you don't expect those little things. It shows that they've got that fun, practical side to them.
"But for actual proper gifts would be things like tea cups and saucers or whiskey glasses. One year I got a lovely water jug.
"What would happen is, for example with the teacups, you would get them maybe two or three years in a row because there would be a whole set to collect.
"I always used to write him a card and give him a gift as well. I remember there was no point in trying to give something fancy. It's difficult when the person has everything.
"But I knew he loves honey so I used to give him a jar of honey or honey fudge or something that I knew he would quite enjoy."
Lunch menu - and unusual second meat
After we see the royals heading back to Sandringham House on Christmas Day, they are set to sit down to a traditional turkey Christmas lunch with all of the trimmings.
But according to Grant, it's not just turkey on offer - but goose too.
He said: "I heard that as well as the turkey, they have goose for lunch which is very traditional and what we had at Christmas before turkeys."
So which side of the debate does he think the royals lie on when it comes to whether it's appropriate to have a Yorkshire pudding on a Christmas dinner?
He explained: "Hand on heart, I don't know. However, I think with the royals, they are quite traditional and if Yorkshire puddings aren't meant to be eaten with turkey, they won't have them.
"So no I don't see them having them with their Christmas dinner and the turkey."
Royal way to toast
Along with the good food, the royals are more than likely to have good drinks to go with it.
And when they look back on the past year, it could be that they propose a toast or raise a glass when thinking about the late Queen.
However, when they drink a toast, there is one common thing that they avoid doing, according to Grant.
He told the Mirror: "I've been at parties with them as a guest and they do raise their glasses and say cheers.
"They might not clink glasses but they will give you eye contact."
Weighing scales game
One of the more unusual traditions it has been rumoured the royals do at Christmas involves weighing scales.
It has been said that the royals weigh themselves on a set of scales when arriving and leaving Sandringham i n a tradition dating back to Edward VII.
Edward wanted to ensure his guests were fed well and any visitors to Sandringham were required to sit on the device and be weighed upon arrival and departure to see if they had put on pounds during their stay.
However it's unclear if it's something the royals still do today, or if it's something to stay in the history books.
But Grant isn't so sure they keep up this tradition and poured doubt on it.
He said: "I've never heard about it. I'm not saying I don't believe it because it sounds like a bit of a fun thing and the aristocracy they do have their fun little games they like to play so that wouldn't surprise me.
"But if I'm honest, I don't quite believe it because I never saw any scales."