Why the John Lewis Christmas ad formula will never, EVER, get tired.

Tis the season for ad agencies to cast cynical glances towards the latest festive offering from John Lewis. And one can understand why.

In a purely creative sense, there really does seem to be a case of diminishing returns here. A full, what, six years on from the first ad that really hit the right notes - the one with the kid waiting not to receive gifts from his parents, but to give to them instead (*sob*) - it does feel a bit like we're watching a washed-up old rock band just repeating the same crowd-pleasing formula slightly less artfully each time, to gradually dwindling audiences.

Except that's only half right. Whilst the work no longer feels fresh, that doesn't mean that the audiences are dwindling. In fact quite the opposite.

Last year's (in my opinion) lacklustre offering with Buster the Boxer was their biggest commercial success to date, making the superior original look like a commercial pygmy in comparison. The trend seems to be continuing this year, with no let up in the torrent of free publicity and goodwill being shown by non-advertising types to Moz the Monster (alliteration is clearly a new "thing" they're trying), so one would imagine that the retailer will be looking back on a similar success come January.

So how is it that this band, with only a couple of its original lineup still intact, arthritic fingers shuddering over their instruments, is somehow managing to shift more records and fill bigger arenas than they did in even their glorious heyday? Such an effect wouldn't be possible with any other advertising campaign, so what gives here?

Well, apologies to all the cynics out there, but it really does come down to the magic of Christmas.

Think about it like this. Does anyone ever ask if Christmas trees have become a bit tired? Or Santa? Or mince pies? Or mulled wine? Or Christmas lights? Does anyone ever question the originality or creative integrity of these concepts? Does anyone ever ask why we don't "freshen up" Christmas?

OK, I'm sure there are some people out there who do feel like that, but I think we can agree they'd get a pretty short shrift from the general public. And that's because one of the central tenants of Christmas is the pleasure of repetition. It's so beloved and cherished precisely because it never changes.

No matter what kinds of craziness are going on in the world at large, there comes a point, once per year, where everything pauses, and we get a sense that everything is OK, everything is where it "should" be.

You can probably recognise this phenomenon in your own approach to Christmas. Don't you do certain things in certain ways just "because that's the way it's meant to be"? That's the way it's always been done? Woe betide anyone who suggests you have a ham rather than a turkey on the 25th. Or who says let's open our presents on Christmas Eve this time. Or who tries to prevent you putting out the tatty decorations you've been using since 1982. Without all this stuff, it's just "not Christmas".

The great triumph of the John Lewis Christmas campaigns lie not in their creativity, and certainly not their originality. No, they've achieved something far far greater than that. They have become a Christmas trope in their own right. You have your carol singers, your mince pies, your Queen's speech, and yes, your John Lewis ad. The public have added it to their arsenal of traditions, and because of that you mess with it at your absolute peril.

If any too-clever-by-half creatives or put-their-own-stamp-on-things marketing directors ever get hold of that account, and don't understand what they have on their hands then John Lewis will take a smacking. People now demand the unabashed sentimentality, the rearrangement of a classic song, the triteness of the whole affair; all because it makes them feel like Christmas. And thus, guess what, John Lewis makes them feel like Christmas too. There are many people who do all their Christmas shopping there for this very reason, because a trip to John Lewis is a festive occasion - and this is purely a result of repetition, not creative bravery.

Just as we are meant to put aside our petty differences at this time of year, so too should we put aside our "marketing best practices". Because Christmas - or more specifically the marketing of Christmas - is bigger than that. In the new year we can all return to wringing our hands about the imperilled state of the advertising industry, funnelling cash down digital black holes, and pinning all our hopes on drones or whatever it is in that moment... but for now let's cherish the one time of year when what advertisers do, undoubtedly, and miraculously, works; when a blockbuster 60 second TV spot unities the nation.

If that doesn't prove Christmas is magic, I don't know what does.