The deception behind this season's televisual event

In some quarters, it is the most keenly anticipated televisual treat of the Christmas period.

No, not the festive episode of Downton Abbey – the one in which Lord Grantham accepts responsibility for the illegitimate child he had with the pastry cook, Lady Mary falls in love with a cousin she never knew existed, Matthew completes his training for the London Marathon, and the entire downstairs staff are wiped out by an unprecedented outbreak of mad cow disease. And not even the Queen's Christmas message (the backdrop may look very similar to Downton, but the plot's a bit more believable, and the dialogue is less stilted). No, for certain households, the launch of the John Lewis Christmas advert is the moment when the whole family gathers around the television and prepares to have its emotions pulled, pushed and twisted over 90 seconds of first-class commercial persuasion.

The advert cost £6m – probably the budget for a whole series of Downton – and stars a seven-year-old boy from Hamilton in Scotland, a soundtrack which comprises a re-working of the old Smiths' song "Please, Please, Please Let Me Get Me What I Want" and a storyline which revolves around an impatient young boy so desperate for Christmas Day in order that – and here's the gut-wrenching twist – he can give his parents presents rather than receive his own.

So far, so sweet. A colleague of mine said that every woman with whom she was watching the ad was in tears by the end, and had to struggle to get their emotions in check in time to boo and hiss Gary Barlow.

Children as altruistic? Well, that's a novel idea at this time of year. But the whole point of a successful advert is that it can change people's behaviour. So, all over Britain, as a result of the John Lewis ad, children are now asking parents for their Christmas list. Don't worry about buying Call of Duty for me, dad, let me get you that set of spanners you've always wanted. Or: let's forget about getting me an iPad2 or an iPhone4s and give the money to charity instead.

The behavioural change that John Lewis are more keen on, however, is to get people down to their stores. The advert has already had 600,000 viewings on YouTube, and its ubiquity on television will probably mean that, despite the economic gloom, John Lewis stores will never knowingly be underpopulated this Christmas.

There have been complaints that the advert is "emotionally manipulative" and "stretches credulity to breaking point". (At least they're not things you could ever accuse Downton Abbey of!) Others have made the point that the cost of production is excessive, and will only fuel higher prices for consumers ("No wonder it's MPs' favourite store," wrote one correspondent). But the real deception of the advert is this: it presumes to be about giving and receiving, whereas it's really about something else: buying.