Though they're most commonly associated with Sloane rangers and stateside factory workers, it is possible to look sharp whilst wearing a down vest.
The main difference between a down vest you can wear and the one your N-Dubz-obsessed nephew wears, is simply how puffy the vest is. The American-influenced versions tend to be far puffier than British versions, meaning they can only be worn as a top layer.
The gillet, however, is essentially a slimmed-down take on the down vest, and consequently is far more versatile. To avoid any fisherman comparisons look for buttons instead of a zip, which will give you a more refined look. Though it is possible to wear a gillet, like the Lavenham version above (£159 from My-Wardrobe.com), as a top layer, it's far better suited to a winter coat and thin knit combo.
We'd recommend teaming it with a John Smedley V-Neck Jumper (£115 from My-Wardrobe.com) and the Aquascutum Navy New Broadgate Tailored Mac (£650 from My-Wardrobe) to get the look.