Media: A Moment with Marquis.(Channel 4 Television Co.)(ITV PLC)(British Broadcasting Corp.)

Last week, the chief executives of ITV, Channel 4 and five wrote to Tessa Jowell, the secretary of state for culture, media and sport, asking her to support Ofcom's position and not ban so-called 'junk food' ads before the watershed.

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 ...