When a jacket-and-jeans combination works well, it is one of the most stylish outfits a man can wear, successfully bridging the casual and the formal, and merging the best elements of both.

It is, however, hard to get right. As mentioned in a previous post on The Newsreader Look, if the jacket and other elements in the top of the outfit are too formal, you can split yourself in half – giving the impression that you only paid attention to your upper torso, because you are going to sit behind a desk on TV.

The key to getting that combination right is making sure the fabrics of the more formal elements – jacket, tie, shirt, possibly handkerchief – are as casual as they can be. So no suit jackets (worsted wool cannot look anything but smart), no silk ties, probably no linen handkerchief and realistically no white shirt.

Two recent photos from the Sartorialist illustrate this very well. The younger gentleman has chosen casual fabrics for everything in his top half: rough woollen jacket; silk, stuffed handkerchief; a wool or cotton-mix tie; and a blue, oxford-weave, button-down shirt. By getting the fabrics right, he has managed to wear both a tie and handkerchief with faded jeans and plimsolls; the ultra-formal with the ultra-casual.

This is one extreme end of the spectrum: every fabric here is the casual choice. He could have opted for one or two more formal fabrics (white shirt, cashmere blazer) and it would still have worked, held in place by the casual material of the shirt and tie. He didn’t have to play it that safe.

The second, slightly older gentleman is at the other end of the spectrum. The shirt is white, of a smooth cotton with a spread collar. It is accompanied by a white, linen handkerchief. The material of the tie is hard to discern, but it is certainly more formal than that of the previous example. The only saving grace is the herringbone jacket.

Now, the jeans are admittedly darker and smarter. So the top half has less work to do in meeting the bottom half half-way, as it were. But the top half is still too pristine. The way the handkerchief is folded so precisely. The flash of a tie clip. It all smacks of dress attire and isn’t suited to jeans.

He wouldn’t have to change much to get my (entirely subjective and arbitrary) approval. Just wear a blue shirt. Or stuff the handkerchief in. Even unbuttoning the shirt collar would save the day.

Jeans and a jacket can easily go wrong. But bear the materials in mind and you’re half way there.