What should actually be in your boot from November to March

Tires first. Everything you put in the boot matters less than the four patches of rubber holding the car to the road, and no amount of kit makes up for bald tread in freezing rain.

In the UK the legal minimum is 1.6mm across the central three-quarters of the tread. Legal and adequate aren't the same thing. Grip in standing water and slush falls away sharply once you're down around 3mm, and that's the point most people who drive in bad weather for a living change them. Check yours with a proper gauge, not a coin, and check all four. The rears wear differently and they're the ones that put you backwards through a hedge.

The tire trade's rule of thumb is that summer compound starts going hard somewhere around seven degrees. Below that it's not really doing its job even on dry tarmac. If you live somewhere that spends four months under that line, or you drive a rural route with a hill on it, winter tires are the single best money you'll spend on the car. All-seasons are the honest compromise: a bit worse than winters in snow, a bit worse than summers in July, and you never have to store a second set or book a swap.

The trade-off nobody mentions: a second set of wheels costs more up front but you're not paying for fitting twice a year, and your good alloys don't spend the winter getting eaten by road salt.

Drive like the grip is borrowed

Smooth inputs. That's most of it. Sudden steering, sudden braking and sudden throttle are the three ways you break traction, and in the cold the margin between fine and sideways is narrow enough that you won't feel it coming.

Brake before the bend, not in it. Get the speed off in a straight line, then steer. Pull away in second if the car will take it. Going downhill, drop a gear and let the engine hold you rather than riding the brakes.

Leave a gap that feels silly. On a wet, cold road, four seconds to the car in front. On snow or ice, ten. Count it off a fixed point — sign, lamppost, gatepost. Most people think they're leaving enough room and are leaving about half.

If the back steps out, look where you want to go and steer there. Come off the brake. Panic braking locks the wheels and turns a correctable slide into a passenger.

And clear the whole car before you move. Roof included. A slab of snow coming off your roof onto the windscreen of the car behind at 60 is somebody else's very bad morning. Lights, number plates, mirrors, all of it.

The kit, layer one: getting yourself moving again

This is the stuff that turns a two-hour wait into a ten-minute inconvenience.

• A folding shovel with a metal edge. Plastic ones snap on frozen slush. You want something that'll clear round the drive wheels and under the sills.
• Traction aid. Recovery boards are the good answer. A bag of grit or non-clumping cat litter is the cheap answer and works well enough on a flat slippery car park. A car mat shoved under the driven wheel has got plenty of people out of a supermarket bay.
• A tow strap, and the knowledge of where your towing eye is. On most modern cars it screws into a threaded point behind a pop-out panel in the bumper, and it lives with the jack under the boot floor. Find yours now, in daylight, on your driveway. People discover the eye is missing at the worst possible moment.
• A lithium jump pack. Better than jump leads because it doesn't need a second car or a stranger's goodwill. One honest limitation: lithium packs lose output in deep cold. Keep it in the cabin, not the boot, when it's properly freezing, and charge it every couple of months whether you've used it or not.
• A tire inflator and a plug kit if your car came with a gunk canister instead of a spare. The canister is single-use and it makes a mess of the sensor.

Layer two: being seen, staying warm

Two of these live in the cabin, not the boot. If you've slid off into a ditch at an angle, you may not be able to open the tailgate.

• Hi-vis vest, in the door pocket. On the hard shoulder at dusk you're close to invisible in a dark coat.
• Torch in the glovebox, ideally a head torch so you've got both hands free. Spare batteries.
• Warning triangle in the boot, for everywhere it's legal to use one.
• Proper gloves. Two pairs: waterproof work gloves for digging and changing a wheel, warm gloves for waiting.
• A wool blanket or an old sleeping bag. Foil blankets are fine as a backup but they're flimsy and they don't do much once you've got wet. A hat matters more than most people think.
• Water and food that survives being frozen and thawed twenty times. Nuts, flapjack, dried fruit. Not chocolate that'll bloom into something horrible by February.
• A power bank and the cable your phone actually takes. Your car charger stops working when the engine does.

If you're running the engine for heat while stuck in snow, get out and check the exhaust tailpipe is clear first, and clear it again every so often. Blocked pipe, fumes in the cabin. That's a real way people die and it's entirely preventable.

Layer three: the unglamorous stuff

Screenwash rated for low temperatures, mixed to the concentrate's cold-weather ratio, not topped up with tap water in October. Frozen washer jets on a salt-smeared motorway are genuinely dangerous.

A decent scraper and a can of de-icer. Never hot water on a cold windscreen — glass doesn't love the shock and neither does your wallet.

A microfibre cloth for the inside of the glass, because winter misting is mostly grease on the screen.

Cable ties, duct tape, a multitool, a spare bulb kit if your car takes the old-fashioned kind. A basic first aid kit, and if you haven't done a day's first aid course, book one; the kit's only as good as the hands using it.

Battery age is the other one. Most car batteries give four to six winters, and they nearly always fail on the first properly cold morning. If yours is past four, get it tested at a garage before the weather turns rather than after.

Keep the tank above half. It's cheap insurance against a two-hour standstill on a closed motorway.

What goes wrong with boot kits

They rot. The jump pack's flat, the food went off eighteen months ago, the torch batteries have leaked, and the shovel is under a pushchair, two camping chairs and a bag for the charity shop.

Pick a date — the clocks going back works — and spend twenty minutes on it. Charge the pack, test the torch, swap the food, check the screenwash, look at the tread. Put the heavy things in a single crate so they're not migrating round the boot.

The whole lot fits in one plastic box and costs less than a single call-out you'd otherwise be waiting three hours for in the dark.

And the calculation changes entirely with children in the back. You can sit out a cold night in a coat. A three-year-old can't, and neither can your father-in-law on the way back from Boxing Day. That's the standard to pack to.