At a fashion event the other day, a buyer introduced me to the concept of the third wardrobe. Most women already have a work wardrobe and an off-duty wardrobe, to some degree – how distinct or blended these are varies enormously, obviously. But now, she said, retailers think in terms of a third category: loungewear.

The third wardrobe consists of clothes to change into when you get home from work. It is what you wear on a lazy weekend morning or to settle in for a boxset on a Friday night.

I am conflicted about this. On the one hand, loungewear might well be my favourite clothing category. If I have been in the office all day, I am quite likely to change into pyjamas within minutes of getting home, even before I have put the oven on. On the other hand, I am uneasy about the third wardrobe as a new shopping category. It’s not as if starchy box-fresh newness is essential, or even desirable.

We can fashion a third wardrobe without a shopping list, revisiting clothes we have, re-homing treasures that languish unworn. Drilling down into the kind of clothes that work for you, figuring out the clothes that make you happy (and your life easier), will make you a smarter and more focused shopper: when you do spend, you will buy pieces you will wear and love for years.

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My third wardrobe (this sounds grand: actually it’s a shelf) operates largely as a kind of fashion retirement home. It is where nice things go to die. A once-luxurious cashmere sweater that the moths have attacked too often. Ancient wool trousers that are still a nice shape, just a bit too bobbly to wear in public. These tracksuit bottoms (pictured) which never quite took as fashion on me, much as I loved the look on other women.

I find loungewear is much more versatile if it’s reasonably nice-looking, not right at the painting-the-house end of its life. Loungewear is most useful if it works for plane or rail journeys, for working-from-home days when you might pop out, as well as in a twilight evening zone.

In many categories, the third wardrobe can be a hand-me-down depository. But I couldn’t live without a nice pair of knitted joggers, with a drawstring waist and a cuffed ankle. That, to me, is the little black dress of this category. It takes pride of place in my loungewear wardrobe. Or rather, on the shelf.