Only a couple of years ago, there was almost no danger of that happening.
Jowell was adamant such a ban would be ineffective in the battle against obesity in children. But political moods swing, particularly when it comes to emotive matters such as fat children, and the TV channels are worried she may change her mind.
The letters make much of the commercial repercussions of a ban: that commercial TV, not just the BBC, provides public-service content and so must be paid for. Consequently, well-funded television can contribute editorially to the battle for a better diet (eg. Jamie's School Dinners).
What the letters do not cover is the principle that products legally and freely available on sale to the public should be allowed the freedom to promote themselves as they see fit, subject to the law of the land and sensible, self-imposed codes.
Is it unduly cynical to suggest that there is little point in appealing to politicians on points of principle? Perhaps, but it is telling that Charles Allen, Andy Duncan and Jane Lighting avoided engaging the battle on those terms. This government has made more incursions into liberties of every description, restricting them in the cause of security or health and safety or racial sensitivity, than any previous one. It is not about to die in a ditch on the relatively puny principle of advertising freedom if it thinks the public mood is in favour of a ban.
Yet this is the crunch issue - we used to pride ourselves on being a tolerant, understanding, unflappable people who indulged others' right to say and do as they wish because we were not easily taken in. Where has all that gone? Now we fuel our growing intolerance by reaching swiftly for the statute book, panic every time we see a problem we don't know the immediate answer to and resort to "action", however futile, in lieu of common sense.
Advertising works, but not in the way many people think. It does not - cannot - brainwash. It makes a case. It sells. Sensible people, including parents on behalf of their children (and, indeed, children themselves), can take that case or, as they frequently do, leave it. The distinction is vital - not just to the advertising business, but to deep-rooted British freedoms that remain, paradoxically, the envy of the world.