Quietly remark within earshot of this ogre that you have won a turkey in your firm's Christmas draw. Suddenly, there is a thunderclap of silence, a patronising stare and a prodding index finger.

"I hope it's not one of them frozen yokes!" he gasps. "If you have any concern for your family's health, you'll lob that fellow into the first passing bin lorry. A master chef would need the patience of a bomb disposal expert to defuse a frozen turkey. So I wouldn't advise an amateur like yourself to try it unless of course you wish to celebrate Christmas stretched out on a slab in the mortuary."

You smile reassuringly and hasten to tell him that your prize is a farm-fresh turkey. But before you have time to blink he strikes.

"Will they never learn?" he sighs. "Do you not know that raw poultry of any kind is one of the most fertile breeding grounds for bacteria? Have you never heard of salmonella?"

To forestall further embarrassment, you comment on the coruscating splendour of a particularly drab looking tangle of fairy lights in a nearby huckster's shop window.

"Wolves in sheep's clothing!" he remarks dismissively. "Those harmless looking baubles have been responsible for more deaths than the Black Plague. They are the Trojan Horses of Christmas. A fellow buys a set of cheap fairy lights, switches them on, and waits wide-eyed for the merry glow. If they don't explode instantaneously or set fire to the Christmas tree, they go on the blink within twenty minutes.

The unfortunate bulb-twiddling amateur with his improvised screwdriver curses the Taiwanese manufacturer and unwittingly prepares to meet his own maker."

At this juncture you should leap onto a passing bus before he launches into his lecture on the properties of the three amp fuse.

The Christmas Knowall has an answer to everything.

"Home-made crackers are more cost-effective than the catchpennies that are on sale in the supermarkets," he declares.

"The roast goose may be more traditional than the turkey but you could float a tanker on the grease that flows out of it.

"The Christmas tree, like the mistletoe, is a pagan introduction - nothing to do with Christmas at all."

On Christmas Eve this Yuletide menace is at his insufferable best. Invading the kitchen, he pesters his already harassed wife with threadbare tales of his traditional Christmas childhood.

Special ways of preparing and cooking hams and Christmas puddings are recited in the painstaking detail that only armchair chefs find interesting.

Comments are passed on the necessity for complementary condiments and wines. Dickens is invoked, as is Bing Crosby, Perry Como and Harry Bellafonte.

"Ah well," he grins as the festive spirit gurgles into his ever-ready glass. "No more shopping days to Christmas! The big day is as close now as it will ever be."

On Christmas Day, students of the Christmas Knowall wait impatiently for his annual pronouncement which is delivered as he rises from the dinner table:

"Christmas is as far away now as it will ever be!" he laughs. "Only three hundred and sixty-five days to next Christmas."

But wait, he is not finished yet. He still has a few hours to go before he delivers his festive farewell. This is the grand traditional retort which is as much a valediction to Christmas as the cuckoo's call is the harbinger of summer.

Go on … ask him. "How did you get Christmas over?"

Right on cue, he will nod his head sagely and reply equally augustly: "Ah …. Quiet as usual, thank God. A day for the family. Sure we'll all be glad to get back to normality."