Never wear navy, don't do matching trousers and avoid feminine styles (yes, really!) The rules to wearing a waistcoat over 50 by fashion expert SHANE WATSON

Don’t know if you’ve noticed but the waistcoat is really having a moment and not just on fit young women with bare toned arms.

As a matter of fact, waistcoats have risen to the top of the easy Outfit Sharpeners. When a jacket’s too hot or too formal, when a blouse is too floppy and not tidy enough, when you need to look a bit more pulled together, that’s when you reach for a waistcoat. Best of all, a waistcoat makes a modern looking outfit out of one or two everyday pieces. What could be simpler!

There are a lot to choose from this summer, including knitted and silk backed styles, but my not-exactly-scientific survey results show that linen waistcoats in cream, ivory, pale blue and grey are in the lead.

Waistcoats are having their moment - seen on fashionistas including actresses Zendaya (left) and Sophie Turner (right)

Women of all ages and shapes are wearing these with matching wide-leg tailored trousers, as part of an extra summery (sleeveless) suit, or with a jacket as part of a three piece suit (not so much of this as, especially in the heat, it can look a bit too trussed up).

Still, far and away the most popular pairing to date, is a waistcoat plus mismatching, loose-fit, tailored trousers. This combination has really taken off among the over-50s and all women who need something easy to wear on a hot day that’s reasonably smart without being restrictive, and at the same time flattering.

Flattering without being revealing is, by the way, the key to the appeal of a waistcoat: a tailored waistcoat gives you definition without clinging to the body. It’s roughly the same principle as a knitted tank top in winter, only it suits more women because it’s structured and you can wear a waistcoat loose-ish and still get the torso-defining benefits.

Meg Ryan shows how great a waistcoat can look when paired with a long, flowy skirt

Still there are times with a waistcoat when you wonder if they look a bit snooker pro, or Gareth Southgate back in the day, and the best way to avoid this is by mismatching your bottom half and avoiding navy. Black always works. Cream is an obvious summer hit, and a cream based pinstripe is great with any neutral trousers.

The White Company's linen/cotton mix cream pinstripe waistcoat

The White Company does a good linen/cotton mix cream pinstripe waistcoat (in the sale £44.50, thewhitecompany.com) with faux horn buttons and a back belt. These classic details are what keep a waistcoat looking chic – you don’t want a girlified waistcoat any more than you want one that makes you look like an England manager.

The White Company also does a linen stretch waistcoat, if you want a slightly snugger fit (in the sale, £55).

Otherwise Marks and Spencer’s version, fully lined with welt pockets (£35, marksandspencer.com) comes with a slightly less deep V neck, which will work better in winter with a plain boyfriend shirt underneath. Get one in ecru or light blue now and one in black for autumn and you won’t regret it.

Besides sticking to a masculine shape, the details to look for in a waistcoat are a V neck (round necks are harder to wear); a V-shaped hemline (straight is far less flattering); and a hip-grazing length – too short and you’ll have a gap between your waistcoat and trousers, too long and you’re into sleeveless jacket territory, and to me they feel more formal. That said I’d make an exception for M&S’s ivory, pinstripe, long-line waistcoat with peak lapels (£49.50); it has trousers to match but I’m thinking it will look great with jeans and tanned arms come September, if all goes well. It’s an incentive to keep lifting those weights, anyway.

The ever-stylish Trinny Woodall wears a three-piece suit with gold high heels

A knitted waistcoat is a more casual, softer option that looks great with long, fluid skirts. This one is from Massimo Dutti

You want to wear your waistcoat now, whatever the style, buttoned up, over a plain open-neck shirt, or nothing at all. Nothing underneath is, naturally, the fashion-forward way to go, and that’s how your daughter’s wearing hers, pretty gold chains in the neckline optional.

If none of this sounds appealing then a softer option, and one which you can layer over a slimfit top, is the knitted cotton waistcoat. This is more casual, but has the advantage of working well with longer fluid skirts if you’re not mad about trousers, whereas a tailored waistcoat plus a midi skirt could make you look like the tambourine player in a Seventies rock band.

Cos has a neat, three-button, ivory cotton mix V-neck waistcoat (£65, cos.com). Otherwise Massimo Dutti has two smart knitted waistcoats, one in a grey marl (£69.95, massimodutti.com), the other in a black and white flecked cotton mix (£89.95, massimodutti.com) in a boxy, edge-to-edge style with ties instead of buttons. In store they’re showing them on mannequins with maxi skirts and soft flowing midis (both £89.95) so something for everyone.

One last thing: a waistcoat is a really useful between-seasons item. Just saying.