Picture the scene: the drawing room at Sandringham, a new group of eccentric in-laws, and an unwelcome, broiling heat in your lower intestine.

That’s what Meghan Markle will experience this Christmas Day, while also having her wardrobe dissected by the national media, her paws grasped by crazed Norfolk folk, and comparisons drawn with Her Royal Glossiness Kate Middleton. Because this year Meghan’s digestive tract will be introduced to Brussels sprouts, and my oh my but is she going to parp.

Those sparkly brown eyes will be introduced to miniature cabbages, and her perfect ears will be informed they grow on 3ft-high trees and despite hailing from Belgium are a staple of British Christmas dinners. She will be encouraged, if I am any judge by a wildly-grinning Prince Harry, to eat as many as possible.

And then shortly after 3pm when the family are gathered to watch Granny’s speech to the nation Meghan will feel something she may only have previously associated with the norovirus: a rolling, bubbling, insistent sort of warmth which indicates the imminent emisson of a most impolite stink.

You can clench. You can count to 10. It may even pass. But it will return with gusto when least expected, and eventually the sprouts will make themselves heard. Meghan knows none of this – Americans go to more effort for Thanksgiving, and have entirely different Christmases. She also doesn’t look the sort to be relaxed about gaseous eructations so will, unlike Harry, probably not see the funny side.

So for Meghan’s information, and for our own further education, here are our Christmas traditions unwrapped, explained, and then hidden at the back of a cupboard for another year.

1. Sprouts

You can’t avoid them

Despite their pro-EU superstate name – and it’s Brussels, not Brussel – originated as wild cabbages in Afghanistan, Iran and Pakistan. They were imported to Europe 500 years ago but didn’t make it across the English Channel until the 19th century, and now Brits eat more sprouts than anyone else – about 40,000 tonnes a year.

They’re great for a number of reasons. They’re full of folic acid, so good if you’re trying to get pregnant. They contain so much Vitamin C that Captain Cook reportedly made his crew eat them to stave off scurvy. And in 2009 Esther Rantzen attempted to set a world record for eating the most sprouts in a minute. She managed 5 – the record was, and remains, 31.

Ancient Chinese physicians once prescribed them for bowel disorders and it’s quite clear why. They contain large amounts of sulphur to deter animals from eating their leaves, and mammals find it hard to digest. It combines with gases already working in our gut to create hydrogen sulphide. If inhaled in large amounts it can lead to death but in small amounts it’s also been found to have anti-ageing properties that protect cells from damage.

What Meghan, and everyone else, needs to bear in mind is this: the reason the Queen leaves the room while her speech is broadcast is not just because it’s odd watching yourself on telly. It’s because she needs to let rip, and Queens can’t be heard doing it. If we all eat the sprouts, we’re all going to do the same. Just don’t be the ONLY one who eats them.

2. Mincemeat

Delicious, but deadly for dogs

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Not mince, and not meat. Sometimes it contains suet which is rice-like grains of cow fat. Can be found in many festive dishes but mainly mine pies, which these days aren’t even pies but pastry cases with something poncy on top rather than further pastry, which is what they should be.

Mince pies were introduced in the Middle Ages by soldiers returning from the Crusades and were originally filled with fruit, spices, and mutton, which must have tasted… special. They were considered Catholic idolatry in the English Civil War (NB Meghan: don’t talk about Catholics to the in-laws, sticky subject) and virtually banned by the Puritans.

Despite this they were imported to the Americas by the self-same Puritans, and became part of Thanksgiving traditions. That doesn’t mean they’re anything Meghan would recognise – some of our less-evolved colonial cousins are still in the habit of using shredded beef and baking them in a single pie big enough to feed the whole family, so she might be amazed to find they’re bite-sized and not nauseating.

Sweet, dried fruit is used in everything from Christmas cake to Christmas pudding, and because they’re very high in fibre it means the whole festive period is tinged with constipation as well as sprout gas. Americans eat Christmas pies made with sweet potato; what an odd lot.

Don’t feed them to the corgis, or any other dog – grapes, raisins and sultanas are toxic to pooches.

3. Christmas jumpers

Bridget Jones's Diary, Colin Firth
This isn’t much of one. Bridget was right

It has of late become normal to don a scratchy, overpriced, possibly-jingly jumper with the sort of embroidery designed to attract, and be forever ruined, by gravy. Charity Save The Children runs a #ChristmasJumperDay fundraiser, with donations encouraged by those wearing one, but in offices up and down the land there are people wearing them without bothering to put a hand in their pocket because there’s an arsehole like that in every office.

They are considered amusing. They are not. Just like:

4. Christmas cracker jokes

“OH HA HA THAT’S SO FUNNY except it’s not”

Even the cracker joke voted the most side-splitting of 2017 is not funny. It’s more wry, the sort of thing that makes you roll your eyes and at best smirk while longing to get stuck in to a plate piled high with indigestion.

Everyone has to read their cracker joke. Even to the point of hunting under the table if it flutters down there before you can grab it, and even though everyone knows it won’t be funny. It’s knowing HOW MUCH not funny it is that is the point.

Christmas crackers don’t really exist in the USA and Meghan will probably be shocked to learn that despite the fact they go BANG! no cracker has ever been involved in a school massacre.

No doubt she will think you get a paper crown if you’re Royal, but not a monarch. If she knew we all got one, she’d be forgiven for thinking we were all Republicans.

5. Divorce

den and angie
“This, my sweet, is a letter from my solicitor… Happy Christmas, Ange!”

It’s not just soapland where family dramas step up a gear at Christmas. The first Monday in January is renowned among lawyers as “Divorce Day” for very good reason. It’s the first day of business after an enforced week or more in the company of one’s other half, the in-laws, the outlaws, and hot sprouts followed by cold sprouts followed by sprout risotto and sprouts in the dog’s dinner. It all gets a bit much, and before you know it someone has decided to withdraw token from board.

The Royals have form on this. Diana and Charles announced their separation in December 1992, and still had to stick out several more shared Sandringham Christmases. Diana announced she had agreed to her husband’s demands for a divorce in February 1996, just weeks after spending the day alone at Kensington Palace. Andrew and Fergie likewise announced their split soon after Christmas, and Princess Margaret and Lord Snowdon went their separate ways 12 weeks after the festive season and 4 weeks after she was pictured in tabloids holidaying with a toyboy lover.

Meghan would be well-advised not to ask about toe-sucking, Camilla’s personal history or whether Philip likes corgis.

6. The tree

I guarantee you did not know this bit

They have Christmas trees in America of course, but it’s likely that Meghan will get a short lecture about how the very first tree was put up at Windsor Castle by Prince Albert in 1841, and was such a hit that trees became fashionable all over the British Empire.

This is true. It does, however, miss out the most important bit which is that actually they are down to MY family and should be called Boniface Trees.

St Boniface was a 8th century Devon-born monk who, after becoming a bishop tootled off to the Frankish Empire to convert the pagans to Christianity. They were at the time prone to worshipping a large oak and in the style of all early Christians piggybacking the new religion in by adapting the previous ones Boniface told them worshipping trees was fine, but this was the wrong one. He said fir trees, being evergreen, were more like the Holy Trinity and then he rather rudely chopped their oak down.

The pagans took exception, and according to some reports nailed Boniface to one of his trees. Then they realised tinsel looked rubbish on an oak tree, converted to Christianity and got into the habit of bringing a fir tree indoors and decorating it to celebrate the birth of Jesus and how sorry they were about Boniface. The Frankish Empire became Germany and Prince Albert brought the tradition over with him when he married Queen Vicky.

There are two further things you do not know about Boniface trees. The first is that royalties are payable to everyone named Boniface at the rate of one piece of chocolate money per tree, and the second is that YOU OWE ME.

7. Boxing Day

Taking a gun into a pressurised space station. What a good idea

The Americans don’t have Boxing Day. They get their sales frenzy out of the way in November, they see no reason to eat yesterday’s food and they think Mike Tyson is a boxer.

But when else are you going to rewatch some of the more rubbish Bond movies? What point is there of wrapping fatty pig sausage products in a fatty pig bacon product and roasting 24 of them in the fat of a bird drier than Roger Moore’s eyebrow if you can’t gnaw them cold 24 hours later? And we all know the only point of cold turkey is to put it on a plate with cold boiled ham, a plethora of condiments and leftover parsnips, while arguing with your family and drinking through yesterday’s hangover.

At Sandringham this day heralds an annual slaughter of wildfowl organised by Prince Philip and enthusiastically joined in with by everyone from the pheasant neck-wringing Queen to the most minor cousin. Meghan, who is considered an animal lover who loathes guns, is going to find that she becomes remarkably well-informed about the ill-advised remake of Thunderball in which Sean Connery’s hairpiece had a starring role.

Here’s another Christmas staple we didn’t have time to fit in

I think we’ve covered all the major points, if not necessarily in the right order. We could go on and explain about the strange Christmas decorations smell which is the lingering pong of the 1980s fashion for spray-on fake snow in a can, which unlike the real stuff never goes away. We could mention Christmas Number Ones which are a strange idea in the USA, why Slade did the best one, Mariah Carey’s done nothing worth noting since, and if they don’t involve any jingling you aren’t doing it right.

We could discuss flying choirboys, snowball cocktails, and why he’s not called Santa. Or perhaps we could explain why the Queen ignores the Twelfth Night tradition and keeps the decs up until February, if only we could understand that ourselves.

But there isn’t time, I’ve mince pies to bake and frankly Meghan has enough problems coping with port after dinner, 7 outfit changes and an extraordinary number of hats.

So I’ll just content myself with saying OF COURSE you put a cross in the bottom of your sprouts, and that backdated Christmas tree tax can be sent to me c/o the Daily
Mirror, Canary Wharf, London E14 5AP.

Have a well-informed Christmas, and a sulphur-free New Year!