Mary Dejevsky: No wonder sales are falling - you can't see the food for the cut-price labels

It's hard not to feel a little bit sorry for retailers, big and small, as they post 40, 50, and now 60 per cent off sale posters in their windows with almost a week of shopping days left before Christmas. If reductions on this scale won't get the great British public spending, whatever will? Maybe, rather like HM Treasury, we have other things to think about and we're just not in the mood. One look at the cluttered aisles of the local Marks & Spencer, though, and the heart sinks to see rail upon rail of winter woollies of such dire shape and colour that even the most desperate present-seeker might fail to buy.

Any sympathy stops, however, at the doors of the big supermarkets. When Tesco announced recently – to a strangely quizzical response – that its sales between September and late November had fallen, compared with the same period the year before, despite a huge price-cutting campaign. I thought I knew why – and why I'd be surprised if Sainsbury's, and maybe others, were not similarly stricken.

Ten days ago, when I did my last Sainsbury's shop, I almost marched straight out again – and would have done, had the fridge at home not been embarrassingly bare. Would-be shoppers currently have to run a gauntlet of orange labels promoting a myriad offers – "second one half price", "3 for 2", "3 for £10", "price-match" with another supermarket etc – all obscuring the actual merchandise. It's often not at all clear precisely what the orange tickets apply to, and, even when it is clear, you need a calculator – or some old-fashioned mental arithmetic – to work out the likely bottom line.

Of course, all this price cutting – which, when you do the maths, can be more show than substance – is all about the supermarkets' "price wars". For the shopper, though, it has made visiting the supermarket an ordeal by pseudo-competition that puts you off the whole idea. On the plus side, I suppose, if the confusion of promotions exhausts us into buying less, it might have the effect of reducing our scandalous levels of food wastage – and, if it does, you could say that they've done the nation a service.

So that's why they had to keep Trident

A month or so ago, there were reports that the United States was unhappy with the planned level of security at the London Olympics. This (speculative) allegation, which suggested American athletes might be scared into bringing their own defensive firepower, spawned a plethora of home-grown claims that the Government and Olympic authorities had severely underestimated security requirements.

Step forward a supremely relaxed-looking Defence Secretary, Philip Hammond, with the comforting statement to the effect that the planned security arrangements were entirely adequate, up to and including surface-to-air missiles. It was the way the expression tripped off his tongue that impressed, as though missiles were an everyday accoutrement of sporting security.

Since then, I've suspected the existence of a special MoD unit, along the lines of party election campaign rebuttal units, whose sole purpose is to drip-feed "reassurance" – if, that is, you find multiples of surface-to-air missiles reassuring – to stay one step ahead of the London 2012 doom-mongers. A couple of weeks later, an equally serene Mr Hammond was on television promising upwards of 13,500 troops – "more than in Afghanistan" – the deployment of several warships, including HMS Ocean, to Greenwich for the duration of the Games, and a squadron of Typhoon aircraft aloft. I think there may also have been talk of dispatching a submarine.

Now I know that Olympic security is no joking matter, but it almost makes you wonder whether the Government had another reason for wanting to retain the Trident nuclear deterrent. Where government media-management is concerned, nothing, but nothing, must be left to chance.

m.dejevsky@independent.co.uk