A good coat is almost never the length you think it is on the hanger. Hold it against you in the shop and it looks right, then you sit down on a train or get in a car and it rides up at the back, or the sleeves creep past your knuckles and stay there all winter. It is worth the ten minutes of standing in front of a mirror properly before you buy, because the right one will see you through every cold morning for years, and the wrong one will sit at the back of the cupboard looking expensive and sulking.
If you own nothing else, start with a plain wool coat in a colour you already wear a lot of, camel or navy or grey, something that sits between the jumpers you already own rather than shouting over them. A wool or wool mix coat gives you the most mileage because it reads as smart enough for work and relaxed enough for the weekend, and it has the weight to feel like protection rather than decoration once the temperature actually drops. A trench earns its slot later, once you have the warm one sorted, because it is doing a different job, a layer for drizzle and transitional weather rather than proper cold. In the shop, check the lining before anything else, a fully lined coat will hang better and last longer than one with a bare seam allowance flapping about inside. Press the fabric between your fingers, a wool that feels dense and slightly springy will keep its shape, one that feels thin and papery will bag at the elbows within a season. Check the button spacing sits where you actually want to close it, not two inches above where your coat naturally wants to meet, and check the sleeve length with your arm bent, not just hanging straight, since that is closer to how you actually move. Shoulder seams matter more than most people think they check, if the seam sits even slightly down your arm instead of at the point of your shoulder, the whole coat will look borrowed.
A wool coat earns its keep from October through to March, over everything from jeans to tailoring, while a trench does the shoulder seasons, the unpredictable weeks in spring and early autumn when you need something but not a proper winter weight. Both work for travel, both work for every day, which is part of why people end up owning more than one.
Try it done up over your thickest jumper before you buy it, not just over a t-shirt, because that is the test that tells you whether it actually fits.
Picked by Fiona Haigh. More in Coats & Jackets.