Four ways to wear: A blazer
The one blazer that looks right at (almost) every occasion
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"At this time of year especially, lots of my clients ask for advice on dressing down a suit – or making a blazer look a bit different after dozens of wears," says Thread stylist Millie Rich. "Guys don't always want the heft of an Oxford or the stiffness of a formal shirt.
"Polo shirts and t-shirts make suits and blazers a bit more comfortable – and one step more casual – for meetings or parties that aren't too buttoned-up. You can wear either type of shirt below with suits, blazers, formal trousers, slim or straight dark-denim jeans and chinos."
Millie's top two alternatives to your usual shirt:
Why it works: "A plain crew-neck t-shirt is so classic and basic, it goes with practically anything. When paired with a suit or blazer, it takes the whole outfit down a notch and makes you look more relaxed."
Best colours: White t-shirts are the easiest to pull off, and they go with any colour jacket. Grey and navy go well with navy jackets.
Things to look for: In order to be smart enough to wear with suits, t-shirts should be crisp and fresh, and not at all transparent. Crew necks are most classic, and you should choose a fit that matches your suit – a slim tee for a slim suit, regular for regular.
Things to avoid: Chest logos; you can sometimes see them under a jacket.
Shoe advice: Go for shoes that are halfway between smart and very formal: brogues, Derbies or minimal trainers.
Why it works: "A polo shirt isn't a huge departure from an Oxford shirt because it still has a collar, but it's more flexible and casual. The combination of a polo and a suit makes me think of two guys: George Clooney and, on the more relatable side, a friend who wore a navy suit with a burgundy polo shirt to another friend's wedding. It was a great look because the colours complemented each other, and he looked smart but different from the rest of the guys."
Best colours: Dark grey, navy, black, burgundy or dark green. A daring guy could even try pink or light blue. Just avoid white, which looks too sporty.
Things to look for: A basic polo in only one colour. Textured fabrics like piqué cotton look more casual than plain cotton or merino wool.
Things to avoid: Button-down collars and very obvious chest logos.
Shoe advice: Brogues and Derbies work well, but trainers make the whole outfit look too sporty.
Thread senior stylist Alice Watt offers advice for guys at different points in the smart-to-casual spectrum.