All havoc can break loose on Christmas Day if anyone dares to try and mess with the lunch routine.

Something as seemingly innocuous as a new kind of vegetable can lead to pained faces and a petulant silence around the table.

So why are we so determined to keep our food traditions rigid at this time of year?

As food historian Ivan Day explains, Christmas Day is the one day when we foodies not only observe tradition, but cling to them.

“Have you ever seen a round Christmas pudding like the ones on Christmas cards?” he asks chuckling, as we discuss festive food.

“They don’t exist any more as they’re all pudding basin shaped. But we like to keep the same pictures on the cards because it’s traditional.”

Daily Echo: Menus of Christmases past

While no one has boiled up cannonball shaped puds wrapped in cloth for decades, the images put on Christmas cards are about pretending we live in the past, says Ivan.

“At Christmas, people hang on to ideas that they don’t even remember. We want to become embedded in tradition. We want a comfort zone in some old warm cosy traditions.”

And this hankering for the past isn’t a new trend. The Victorians were just as nostalgic at Christmas for their treasured past, he says.

Queen Victoria discovered that in the 17th century boars heads were eaten at St John’s College, Cambridge. So she bred them on her estate and sent boars heads to her various children all over Europe.

Daily Echo: Menus of Christmases past

“It’s just like today, lots of people think about cooking goose, because that’s what Tiny Tim ate. We like to draw on the past at Christmas.”

But although in 2009 we’re still eating many of the same dishes our ancestors would have eaten, they’ve subtly changed over the years, Ivan explains.

“By 1900 the original method of making mince pies had died. Cooks stopped putting in meat and added currants, raisins, candied peel, spices, lemon, lemon juice, alcohol and suet instead. But before that mince pies were meaty and fantastic – and they used to make them in the most amazing shapes.”

But while we may have lost a few foodie delights along the way, at least these days it's not only the rich families who get a decent feed.

In the days before the fan-assisted oven, the Christmas bird needed to be cooked in front of the fire, says Ivan.

And this led to massive inequality on Christmas Day.

“Wealthy families would have their own own rotisserie systems, but the less well-off had to come up with more inventive methods of cooking their lunch,” he says.

“If you were really poor and didn’t have a fireplace, you’d take your Christmas bird to the bakers, and for a penny they would bake it in the ovens.

“There are stories of Victorians waiting in a queue outside bakeries waiting for their Christmas dinner.”