On a bad day, a good coat should shut out the world. Snappy three-quarter-length car coats are all very well with trousers, but it is a patient, not to mention skilful, woman who can make them work with long skirts.
With the long coat, on the other hand, there's no need to worry about proportions. On those rare occasions when your outfit has gone badly wrong, the long coat will just glide over the top of everything - and that means everything. When investing in one, take any long skirts you have into the changing room so that you can make sure none of them is longer than the coat.
Happily, for the first time in ages, there are plenty of tempting long coats to choose from this season, at all levels of the market. Not that price should be the sole consideration.
An expensive one will probably last and feel wonderfully soft, but if you're thinking of opting for a high-fashion statement - an all-out military number, or lashings of cat print trimming, for example - perhaps this is not the season to go for broke.
It could even be the winter when the coat-rails in the markets and army surplus stores come back into their own. Failing that, the high street has plenty of inexpensive, but plausible, versions: try Principles, Jigsaw and Next for fake fur trims; and Marks& Spencer for its pillar-box red, military long coat with black velvet buttons (125).
One word of caution, however: not all cheap fake furs turn out to be a bargain. The kind that takes on a neon quality is to be avoided at all costs. If it looks like that under the shop lights, in two weeks' time it will look well and truly dreadful.
The camel coat (in anything from deep cream to toffee-coloured) is the all-time classic: the one which, when you have got it right, will look effortlessly glamorous in a Grace Kelly, shrugged-on sort of way; and if you've got it wrong, dowdy in an oh-dear-how-dull sort of way.
To avoid the frump factor, it is worth investigating the different variations that the designers have been coming up with this season (everyone from Armani to Nicole Farhi, whose buttonless, kimono-style one is shown here, has had a go).
The trick with the camel is not to skimp. This is a versatile coat that looks good in the town or the country - with jeans or over a suit - and will go on for ever. The cut should be generous - but that does not mean buying the next size up - and the wool should look plush and glossy.
The weight of a coat, ultimately, could make all the difference between something that you enjoy wearing and something that becomes a necessary evil as winter progresses.
The fact is that in many British cities, people who spend their lives rushing in and out of heated buildings and cramming themselves into overcrowded public transport do not need a coat that is too thick or cumbersome.
What they do want is something cosy and enveloping that will work as part of a layer-dressing policy (over a jacket or a tunic jumper, for example); something that is lightweight without being flimsy.
Ideally, that means wafting around in pure cashmere (a 100percent cashmere coat can be folded into a tiny parcel yet keep you warm in deepest Siberia). But if finances will not stretch that far, track down a wool-mix that has as high a cashmere content as you can afford.
If, however, you live in the country, spend a lot of time in the open air or simply like the idea of a coat that will keep you warm, even if you are naked underneath, the new sheepskins - soft as clouds and in mouthwatering shades - are hard to beat. One way or another, this winter's fashion has you covered.