Every season the fashion industry crowns a new saviour. This year it is striped trousers - and unlike most such coronations, this one makes sense. Not because they are new, but because they are most likely already sitting somewhere in your wardrobe, untouched since last summer.

The argument is practical: stripes look fresh, they lengthen the line and they bring character to an outfit that would otherwise be dull. Stylists phrase it as even the plainest pairing gaining something of its own. Translated into language that has nothing to sell: with these you do not have to think much, and you look like you did.

What actually changes the picture

Of the ten suggested looks, three work without a single newly bought item. A white shirt with striped trousers is a combination as old as the shirt itself, and it is still the safest way for nobody to notice you are wearing the piece for the third time. A waistcoat instead of a T-shirt makes a difference that costs nothing if you already own the waistcoat. A scarf tied in place of a belt is a trick that changes the entire outfit without spending a euro.

The rest depend on what you already own: a raffia hat for a Mediterranean note, colourful trainers for a more relaxed version, embroidery or a floral blouse for something softer. The ones with diagonal stripes visually lengthen the figure - that is geometry, not marketing.

The two versions that demand attention

A matching set in the same fabric looks expensive and is the fastest route to looking put together, but it is also the fastest route to looking like pyjamas if the cut is wrong. And the sequinned version, inspired by the seventies, only works if everything around it stays calm - usually with a menswear-cut shirt.

That is the main lesson of the whole list: not one of these looks requires a new wardrobe. It requires one item most people already own, and a bit more nerve in the combining. That is the real advice. Everything else is a shopping recommendation.