When all the presents are bought for the children, the house is decorated and the old man got jipped out of his Christmas bonus ... there's no money left in the kitty for a turkey or ham so mom has to go out and buy a couple cans of Spam for the Christmas day meal. She boils up a few potatoes, cooks up some squash and bakes some short-breads for desert. Dad feels bad because he's all tapped out and can't afford a nice gift for the old lady who pretty much takes the brunt of abbuse 365 days a year ... drunken beatings, carrying him home from the pub on dart night and hauling his ass out of the klink after a good old fashioned soccer brawl or six. So as a present for his dear old gapped-tooth - hooked backed missus, dad dresses up as Santa covers mom's backside in spam and lays a good old fashioned Christmas ass banging on her ... balls-deep.
Of course in the British tradition of not really being too overly affectionate or loving ... its almost always a quicky over the kitchen counter or table while mom continues with the meal with her housedress thrown up over her head.
Made popular in the early 1960's in the Nottingham and Worcester regions.
Also popular in Leeds where dental hygiene is so poor oral sex is virtually impossible.