Unwrapping Christmas: familiar traditions that surprise us every year

I wish it could be Christmas everyday", sang Wizzard in 1973, and we shall soon be hearing the refrain again and again as DJs reach down their collection of festive numbers. Perhaps as the co-author of a book on Christmas I should share the sentiment; it may be good for sales.

Nevertheless, although Christmas may come but once a year, the preparations - notoriously - go on for several months and the "expert" on Christmas - like the Santa Claus who works an annual shift in a department store - is suddenly in demand for a season.

It's as if, every year, Christmas is happening for the first time. Just before the plunge into our major festival, the media ponder the nature of the modern Christmas. How did we develop a festival with so many sides to it and so many contradictions? Months before we start unwrapping our presents, Christmas itself is annually unwrapped.

Deconstructing our major festival is fun, for there are layers upon layers of wrapping around Christmas and the way we celebrate it, and the season provides opportunities to place articles and give lectures.

I've lectured on the subject at the British Museum, to Historical Association branches and to local history societies. When introducing an audience of Japanese housewives whose husbands were working for Japanese firms in the North East to the English Christmas, I found that much was familiar to them because in Tokyo department stores White Christmas will be playing and you can arrange for Santa Claus himself to visit your home.

By early December, the pace is hotting up and I find myself, like some temporary Father Christmas, doing an annual performance. There are calls from journalists wanting information for their seasonal articles and from radio stations asking me to contribute to early morning programmes. The latter can be fun, although it's not always easy to summon up the seasonal spirit at 7.30am when you are rung up and asked to stand by until after the announcements about roadworks and traffic delays.

A relentlessly cheerful and opinionated anchorman introduces questions for discussion: does Christmas shopping start too early, has it become too materialistic, what is the origin of the Christmas cracker, and how did Boxing Day get its name? A final question is often: "Do you enjoy Christmas yourself?" You begin to wonder ...

You start to empathise with the central figure of the modern Christmas, or at any rate with the army of part-timers who represent him in department stores.

Standing before television cameras and surrounded by Christmas shoppers, I have pontificated as the obligatorily jovial spirit of the modern Christmas sits in his grotto, gingerly greeting wide-eyed innocents and sceptical little monsters with the same ersatz good humour and bonhomie. Is he the American Santa Claus in a red suit with a great buckled belt, or an English Father Christmas in a long hooded robe? An annual count should be made as to which is predominant.

I settle into my role, critically assessing innovations: those houses lit up like ships awaiting review, with Santas and reindeer on the roof and no thought of the January electricity bill; and the way that pop songs of past decades seem to have become as much a part of the festival as carols. Brenda Lee is still Rockin' around the Christmas Tree as she's been doing since 1958, and what would DJs do without Slade's Merry Xmas Everybody?

There's never a shortage of stories to comment on, even if many are much the same as last year's: some council will have decided that it's Winterval rather than Christmas and some idiot headmaster will have banned Nativity plays from his school; somewhere in Germany or France an American Santa Claus will have been run out of town in favour of a more native St Nicholas or Pere Noel; and an eccentric will have been unearthed who does celebrate Christmas every day.

I rapidly become a Christmas nerd. Are more geese being sold this year and have frozen turkeys taken over from fresh ones? Is the office or departmental Christmas party, at which drink reveals unexpected lusts, doomed in a litigious age?

Settling into my hotel room after delivering one of my party pieces, I switch on the television, only to find a programme made more than a decade ago about Christmas. It includes, rather unnervingly, an interview with my younger self. I've become part of Christmas past.