It clicked on a day I was supposed to be travelling light. Laptop, a change of shoes, a wet umbrella, a sandwich that leaked through its bag and somehow still ended up fine because everything had its own compartment and nothing touched. I'd spent years carrying a tote with everything loose at the bottom like a jumble sale, and that was the first time I got off a train and thought, right, I'm never going back.
Before you buy one, it's worth checking a few things the photos never quite show you. How the straps actually sit, padded or not, because a thin strap on a heavy day feels like being told off by your own shoulder. Whether the back panel is padded too, since an unpadded one presses every zip and corner of whatever's inside straight into your spine. Look at what the bottom is made from, because canvas looks lovely until you put it down on a wet pavement outside a café and it drinks the puddle. Leather and leather look alikes cope better there, and a vegan leather base with a canvas body gives you the best of both without the bag weighing as much as the laptop inside it. Check the zips are the chunky metal kind rather than the thin plastic ones that catch and then just stop working one day, usually when you're late.
On colour, I've made my peace with the fact that pale ones look wonderful for about three weeks. A light tan or a stone colour photographs beautifully and then meets a bus seat and that's that. Black is the obvious answer and it is boring, I won't pretend otherwise, but it goes with everything and hides the ink stain from the pen that always seems to explode in there. A proper dark brown does the same job with a bit more warmth to it. If you want some personality without the maintenance, a deep green or a burgundy in a slightly textured fabric hides scuffs far better than anything smooth and pale ever will.
If you've got none of these and you're starting from nothing, go for a mid sized one in a structured fabric, something that holds its shape when it's half empty rather than slumping into a sad little sack, with a laptop sleeve even if you don't currently own a laptop, because you will end up carrying someone else's at some point. The mistake is buying the huge one because it looks like good value for the extra space. You will fill it, every time, with things you didn't need to bring, and your back will know about it by the second stop on the train.
Picked by Leanne Doyle. More in Bags.